iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Antihost offers Linux VPS plans with full root access, unlimited traffic on a 1 Gbps port and a 14-day free trial.
A send-only iRedMail server is not a separate iRedMail installation mode. It is an iRedMail/Postfix configuration that accepts messages from approved local applications or clients, sends them to an authenticated upstream relay (smart host), and does not provide public inbound delivery for its own domains.
The safest setup is to configure Postfix’s relayhost, protect the SASL credential map, restrict mynetworks and iRedAPD to the systems that should submit mail, and then verify both successful delivery and rejection of unauthorized relay attempts.
What “send-only” means in iRedMail
iRedMail packages and configures Postfix, but “send-only” is not a selectable iRedMail product mode. In practice, the server performs three jobs:
- It accepts mail only from local applications, the loopback interface, or explicitly permitted LAN clients.
- It forwards every accepted message through an authenticated upstream SMTP service instead of delivering directly to recipient MX servers.
- It does not act as a public mailbox or inbound destination for its hosted domains.
The upstream service is often called a relayhost or smart host. It may be a corporate SMTP gateway or a transactional relay. The upstream service, not your Ubuntu host, normally performs the final Internet delivery. Whether this arrangement is preferable to a minimal standalone Postfix relay depends on whether you need iRedMail’s administration, policy, and local-service integration; the available evidence does not establish a universal winner.
#1 Best Overall
- Powerful Turbo Fan:CAGIWIRU Electric Air Duster have reached speed up to 130000RPM,Can efficient remove dust and debris.With LED light and Three Adjustable Speed to meet with different cleaning tasks.
- With Attached USB C Fasting Charging cable.Charing 3 hours,Enjoy up to 240 minutes of use on the lowest setting, For third speed can use for 25mins.with four charging options to meet with your needs.
- Wide Application:Upgraded attached 5 different nozzles,making it suitable for a variety of scenes, such as car,pet, pc, keyboards, and other electronic devices. It also serves for office and home clean duster.
- Handy Design & Portable:Cordless air duster electric nozzle is Light weight and small size, design and comfortable to hold and space saving, convenient to carry around. You can put it in your room or inside the car without taking up space.
- Warranty & Support: Our Electric air duster comes with 5 years warranty and 24/7 customer service. During this period, if you have any questions,pls kindly feel free to contact us.
Prepare the Ubuntu and iRedMail installation
Start with a working iRedMail server
Install iRedMail on a supported Ubuntu system and complete its normal initial configuration first. This guide changes the generated Postfix and iRedAPD settings; it is not an installation procedure. Record the iRedMail release and the installed Postfix version before editing files, because parameter names and generated include files can differ between releases.
Decide who may submit mail
Write down the exact senders that need access: for example, the local machine only, a private application subnet, or a short list of application hosts. A send-only server should not be an open relay. You will express this policy in both Postfix’s mynetworks and iRedAPD’s MYNETWORKS setting.
Recommended Free Tools
Collect upstream relay details
- SMTP hostname supplied by the relay operator.
- Submission port. The configuration examples in the available documentation use port
587. - Username and password, or another SASL credential accepted by the upstream service.
- The sender addresses or domains that the upstream account is authorized to use.
Do not assume that port 587 is mandatory for every provider. It is the port used in the cited examples; the reason for choosing it over port 25 is not established by those sources, so follow the upstream service’s current requirements.
Inspect the active Postfix configuration before changing it
iRedMail may already use MySQL or MariaDB maps and generated configuration fragments. Inspect the effective configuration rather than replacing files blindly:
postconf -n
postconf sender_dependent_relayhost_maps
postconf mynetworks
postconf inet_interfaces
postconf -n prints non-default settings. The second command is especially important: if it returns an existing proxy:mysql: map, editing main.cf to point at a new hash map can disable iRedMail’s existing sender-dependent lookup. Save a copy of the current configuration and note which file supplies each setting before proceeding.
Configure one upstream relay for all outgoing mail
Set the relayhost
For a single upstream service, set relayhost in the active Postfix main.cf:
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Rank #2
- Screen Cleaner is Your Screen’s New Bestfriend! - EVEO is proud to present a screen cleaner that’s perfectly suited for your TV. Meet your new screen cleaner, computer screen cleaner, laptop cleaner, iPad cleaner, Macbook,tv cleaner or any other electronic device. Our screen cleaner spray and wipe along with the included plush microfiber cloth, easily removes dust, fingerprints & other smudges on the screen’s surface. Clean effectively for a streak-free screen
- Gentle on your Screens - Our screen cleaner spray and wipes is compatible to be used even for the most sensitive LCD, LED, CRT, and OLED screens in proper use. Be at ease knowing that this product is compatible with all the major brands: LG, SONY, Samsung, Sharp, iPad, iPhone, Android screens, Kindle, PC monitors - we’ve got you covered! Can be used as LCD screen cleaner, tv cleaner, smart tv screen cleaner, and more
- Premium Super Soft Plush Microfiber Cloth - Included in this efficient screen cleaning kit. This screen cleaner spray and wipe has our signature plush microfiber cloth specially designed to comply with screens and monitors and leave them streak-free. Has been shown to effectively absorbs stubborn stains, zero streaks, and no fiber shedding. Always use this together with our screen cleaner for the best results
- Easy-to-Use Screen Cleaner Kit + microfiber cleaning cloth - The EVEO Screen Cleaning Kit will easily be your new favorite tool when it comes to taking care of the things you love most, quick and easy solution for a streak-free screen. Simply screw on the sprayer gun on the screen cleaner bottle. Spray the cleaning liquid onto the microfiber cloth, then wipe the screen until desired cleanliness & shine is achieved.
- Quality Screen Care Kit Worth Purchasing - Enjoy a convenient Screen Cleaner anytime, anywhere you need it. Your satisfaction is our top priority. We stand behind the quality of our products and that’s why, you shouldn’t be worrying at all. We manufacture the Best Screen Cleaner. and can be used for laptop cleaning kit, laptop screen cleaner, tv screen cleaner for smart tv. MacBook screen cleaner, monitor cleaner or screen cleaner spray for electronic devices with microfiber cleaning cloth
relayhost = [smtp.example.com]:587The square brackets are significant: they tell Postfix to connect to that hostname directly instead of performing an MX lookup for it. Replace the example hostname and port with the values supplied by your relay operator.
Enable authenticated SMTP
Create a password map containing the upstream login. The path below is a conventional example; use the path already referenced by your installation if it differs:
[smtp.example.com]:587 relay-user@example.com:REPLACE_WITH_SECRET
Store that line in a root-owned file such as /etc/postfix/sasl_passwd, then compile the map and lock down both files:
sudo chown root:root /etc/postfix/sasl_passwd
sudo chmod 600 /etc/postfix/sasl_passwd
sudo postmap hash:/etc/postfix/sasl_passwd
sudo chmod 600 /etc/postfix/sasl_passwd.db
Reference the map and enable SASL in main.cf:
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
noanonymous prevents anonymous SASL mechanisms. Do not paste a real password into a support ticket, shell history, article, or log. If the relay operator rotates the credential, update the source file, rerun postmap, and reload Postfix.
Check the resulting settings
postconf relayhost smtp_sasl_auth_enable smtp_sasl_password_maps smtp_sasl_security_options
Confirm that the displayed map path exists and that the database file has a current timestamp. A correct source file with an old .db file will still authenticate with stale or missing credentials.
Route different senders through different relays
Use sender-dependent routing when different domains or addresses require different upstream credentials or gateways. Postfix supports smtp_sender_dependent_authentication = yes and a sender-dependent relayhost map. The sender-dependent map is searched by envelope sender; a default relayhost can remain as a fallback.
Rank #3
- 【Large size】：Measuring 800 x 300 mm/ 31. 5×12 inches, which is wider and taller than others. Large mouse pad can perfectly fit your keyboard and mouse of any size, and there is also ample space for peripherals such as phones, tablets, etc.
- 【LED backlight mouse pad】：Blade Hawks RGB mouse pad provides 7 static modes and 7 dynamic modes will give you the options you are looking for. Power-off memory function remembers the last lighting mode you selected. The super glow fiber Chroma will give you a colorful gaming setup that you want.
- 【Anti-slip rubber base】：Made from Natural rubber, this gaming mousepad will firmly grip your desktop, allowing you to enjoy the ultimate precision in the games you are most passionate about. It also comes with a texture that enhances this ability even further.
- 【Smooth and waterproof surface】: Micro-textured cloth surface, for extremely precise mouse control and a smooth movement. When liquid splashes on the gaming mouse pad, it forms water droplets and slides down. Will not delay your work or gameplay.
- 【Plug and play】: This mouse and keyboard pad is powered by USB, plug and play, no driver required. One button control light modes. Press one time to change the lighting mode, press twice to change the brightness, press and hold about 3 seconds turn ON/OFF.
First preserve iRedMail's existing map
Run:
postconf sender_dependent_relayhost_maps
On many iRedMail installations, the result points to a MySQL/MariaDB lookup, commonly represented by a path such as proxy:mysql:/etc/postfix/mysql/sender_dependent_relayhost_maps.cf. That path is an example of the generated layout, not a value to assume on every release. Do not overwrite it without understanding the database query and the records it serves.
Use a hash map only when you intentionally replace or add to the current design
A documented Postfix example uses a hash map that associates a sender domain with a relay on port 587:
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →example.org [smtp.example.com]:587
If your installation is designed for a file map, save the entry in the configured map file (for example, /etc/postfix/relayhost_maps) and compile it:
sudo postmap hash:/etc/postfix/relayhost_maps
Then enable sender-dependent authentication and point Postfix at the map that your design actually uses:
smtp_sender_dependent_authentication = yes
sender_dependent_relayhost_maps = hash:/etc/postfix/relayhost_maps
Do not copy those two lines over an existing iRedMail MySQL setting simply because the file-based example is easier to read. If you need database-backed per-sender routing, add the appropriate records through the existing iRedMail data path and verify the generated lookup. The exact SQL schema and administration workflow are version-dependent and are not established here.
Provide credentials for each sender or relay
The SASL password map must contain keys that match the sender-dependent lookup behavior configured on your server. The Postfix small-office guide describes searching the password map by sender before falling back to the destination or default relay. Test each sender identity separately; a message from one domain succeeding does not prove that another domain has a matching credential.
Rank #4
- 【Softer and More Comfortable】Vaydeer wrist rest has unique diamond pattern, which is the combination of softness and aesthetics. The materials of wrist rest are improved into higher quality memory foam and covered with silky smooth lycra. The computer wrist rest makes you as comfortable and cushiony as like rest your wrists on clouds.
- 【Ergonomic Wrist Saver】The wrist rests for keyboard and mouse comes with a 17.32×3.15×0.83 inch keyboard wrist pad and a 5.94×3.15×0.83 inch mouse wrist support. Based on ergonomic design, the unique concave shape is the perfect fit for your wrist joints. The wrist rest pad fits most computer keyboards and laptops, improve hand and wrist posture, release your wrist and arm stress.
- 【Non-Slip Rubber Bottom】Featuring an anti-skid silicone base on the bottom, this wrist keyboard support stays firmly in place on your desk, preventing the padding from sliding around, ensuring stable and consistent wrist support during extended computer sessions.
- 【Better Experience & Pain Relief】Our keyboard arm rest is beneficial to alleviate the soreness caused by direct contact and friction between your arm and a hard desk surface, reducing the risk of wrist fatigue or carpal tunnel. The soft texture of memory foam can evenly distribute the pressure around your wrists and provide good support with just enough give.
- 【Helpful in Multiple Scenarios】Whether you're working, studying, writing, typing, gaming, this keyboard and mouse rest combo is an essential accessory to add comfort and support to your hands and wrists. It’s also a great gift for men, women, family, friend, coworker, gamer, teacher, etc.
Do not use the wrong iRedAdmin control
An iRedMail forum answer warns that per-domain relay settings in iRedAdmin apply to received mail, not outgoing mail. They therefore do not, by themselves, configure sender-dependent outbound routing. Verify the effective Postfix map with postconf and a real test message instead of relying on an apparently similar administrator-panel field.
Restrict the server to approved clients
Set Postfix's mynetworks
Postfix uses mynetworks to identify trusted client networks. Include only loopback and the specific application addresses or private subnet that must submit mail. Avoid broad public ranges:
mynetworks = 127.0.0.0/8, [YOUR_PRIVATE_SUBNET]
Use the syntax already present in your generated configuration and confirm the result with postconf mynetworks. If applications run on the same host, loopback-only trust is easier to audit than permitting an entire LAN.
Match iRedAPD's MYNETWORKS setting
The allowed network must also be present in iRedAPD's MYNETWORKS setting, commonly located in /opt/iredapd/settings.py. Check both files for the same intended addresses. A mismatch can produce confusing results: Postfix may trust a client that iRedAPD rejects, or iRedAPD may treat a network as trusted when Postfix does not.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Limit listening interfaces
If only local applications submit mail, configure Postfix to listen on loopback through inet_interfaces. If a private application host must connect, listen only on the required private address and protect it with the host or network firewall. The generic Ubuntu relay pattern uses loopback-only listening for a local relay. Do not expose an SMTP listener on a public interface merely because the package enabled one by default.
Keep inbound delivery out of the design
A send-only host should not be advertised as the public MX for domains whose mail it is not meant to receive. Review the active virtual-mailbox and recipient configuration generated by iRedMail, remove unintended public reachability at the firewall, and ensure that no external host can submit unauthenticated mail. The goal is operational, not cosmetic: the server must accept messages from the approved submission sources and reject relay attempts from everywhere else.
Best Value
- 【No Drill Mounted】Cable management tray can be assembled in as little as 3 minutes or less-simply. Side clips easily clampe the edge of desk, pass through the holes on the sides, and secure excess cables with baskets. Desk cable management supports inward or outward installation to meet your needs in different scenarios, and provides you with great convenience when collecting and organizing wires.
- 【Rubber Pad Protects Desk】Wire organizer under desk built-in soft rubber pads on the clamp protect your desk from scratches, so you will not damage your furniture or office.
- 【Sturdy and Beautiful】Cord management under desk is made of high-quality carbon steel and holds about 15 lbs. The wire basket has 2 holes on each side of the tray to enable your cables to pass freely. Cable baskets are suitable for desk thickness use from 0.4" to 2.4".
- 【Space Saving & Keep Organized】Desk cable management tray holds all your power cords, outlet strips, USB hubs and computer transformers hidden from your feet, and the data cables will not enter the vacuum cleaner to keep your desk clean and tidy. Desk wire organizer is also suitable for use in the kitchen and outdoors.
- 【Reduce Safety Risks】Cable tray under desk keeps all plugs away from your kids, no more worry about tripping. Using 2 holes wire tray saves extra space, helps you easily cabling and wire protection. The mesh design is not easy to accumulate dust, but avoids safety accidents caused by messy wires.
Apply the configuration safely
- Validate the Postfix syntax and map files before reloading:
sudo postfix check
- Rebuild every hash map whose source file you changed. For example:
sudo postmap hash:/etc/postfix/sasl_passwd
sudo postmap hash:/etc/postfix/relayhost_maps
- Review the effective values:
postconf relayhost sender_dependent_relayhost_maps mynetworks inet_interfaces
- Reload Postfix so it reads the new settings:
sudo systemctl reload postfix
- If you changed iRedAPD's settings, follow the service-management procedure for the installed iRedAPD release and confirm its running configuration. Do not assume a Postfix reload reloads iRedAPD.
Keep the previous configuration available until a complete send-and-reject test passes. A reload normally preserves queued mail; nevertheless, check the queue and logs after every change.
Test delivery from the server
Send a controlled message
Use a recipient address you control and an envelope sender that the upstream account is authorized to use. The local sendmail-compatible interface is sufficient for a basic test:
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallprintf 'Subject: iRedMail relay testnnTest messagen' | sendmail -v recipient@example.net
For a sender-dependent setup, repeat the test with every configured sender domain. A successful local handoff only proves that Postfix accepted the message; it does not prove that the upstream relay authenticated or delivered it.
Inspect the mail log
Watch the mail log while sending:
sudo tail -f /var/log/mail.log
Look for the queue identifier, the selected relay hostname and port, SASL authentication success or failure, and the final remote status. On systems that route Postfix messages through systemd's journal, also inspect:
sudo journalctl -u postfix --since '15 minutes ago'
A queued message with repeated deferrals means the upstream service has not accepted it yet. Read the enhanced SMTP status and the relay's policy explanation before changing local restrictions.
Prove that unauthorized hosts cannot relay
From a host that is not in mynetworks, attempt an SMTP submission without valid authentication. The server should refuse relay rather than queueing the message. Perform this check from outside the trusted LAN as well as from an untrusted address inside it if your network has multiple paths. Record the test date and the configuration revision so future changes can be compared.
Free tools Windows power users keep installed
One-click scans. No signup required.
Common failures and precise fixes
| Symptom | Likely cause | What to check |
|---|---|---|
| Postfix tries to deliver directly to recipient MX servers | relayhost is empty, overridden by a later configuration fragment, or a sender-dependent map returns an unintended value. |
Run postconf relayhost sender_dependent_relayhost_maps and inspect the queue log for the selected destination. |
| Authentication fails immediately | The password map was not compiled, its key does not include the port, or the secret is wrong. | Confirm the exact key (for example, [smtp.example.com]:587), rerun postmap, check permissions, and rotate the upstream credential if necessary. |
| One sender works but another is deferred | The sender-dependent map or SASL map has no matching entry for the second envelope sender. | Test each sender separately and verify the active map with postconf; do not assume the global fallback is being used. |
| Changes in iRedAdmin have no effect on outgoing mail | The panel setting controls received mail rather than sent mail. | Configure Postfix's outbound relayhost or sender-dependent map and verify with a live message. |
| Local applications cannot submit | Their address is absent from mynetworks, iRedAPD's MYNETWORKS, or inet_interfaces does not listen on the required address. |
Compare all three effective settings and check the host firewall. |
| A public host can submit mail without credentials | The listener is exposed and relay restrictions or trusted networks are too broad. | Remove unintended networks from mynetworks, restrict listening interfaces, review iRedAPD's trusted networks, and repeat the external rejection test. |
| The map appears correct but Postfix ignores it | The database file is stale or a generated MySQL map is still the active setting. | Rerun postmap for file maps and use postconf to identify the map Postfix actually loads. |
Operational and security checks
- Protect credentials. Keep the plaintext SASL file readable only by root, protect the compiled database, and rotate credentials according to the upstream relay's policy.
- Use least privilege. Trust loopback or narrowly defined private addresses instead of an entire public range or an unnecessarily large LAN.
- Monitor the queue. A send-only server can accumulate mail when the upstream relay is unavailable or rejects a sender. Investigate deferrals rather than repeatedly resubmitting the same message.
- Check sender authorization. The upstream service may permit only verified domains or addresses. Match the envelope sender to those permissions during testing.
- Preserve generated configuration. iRedMail upgrades or configuration tools can regenerate files. Keep a record of intentional relayhost, map, network, and interface settings and recheck them after upgrades.
- Test after network changes. A changed private subnet, firewall rule, or container address can silently move an application outside both
mynetworksand iRedAPD'sMYNETWORKS.
iRedMail outbound configuration or standalone Postfix?
For a host that only submits application mail, a standalone Postfix relay may have a smaller maintenance footprint. Keeping iRedMail can make sense when you already depend on its administration, policy controls, account database, or other integrated services. The evidence available for this guide does not verify a general performance, security, or feature advantage for either choice. Decide based on the services you actually need, then apply the same principles: authenticated upstream relay, narrowly scoped trusted networks, limited listening interfaces, and an explicit test that unauthorized clients cannot relay.
Quick Recap
Final verification checklist
postconf -nhas been saved and reviewed.relayhostpoints to the intended upstream host, with brackets and the required port.- The SASL password map is compiled, protected, and referenced by
smtp_sasl_password_maps. - Any sender-dependent map was inspected before being changed, especially an existing MySQL/MariaDB lookup.
mynetworksand iRedAPD'sMYNETWORKScontain the same intended clients.inet_interfacesand the firewall expose only the interfaces required for submission.- A test from each sender identity authenticates and reaches the upstream relay.
- An unauthenticated external host is rejected and cannot place mail in the queue.
- Logs and the queue show final delivery or a clear, actionable upstream error.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
