Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors?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 reinstalliTechGuides 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.
Configure Postfix as a local mail-transfer agent and set Mailgun as its authenticated smarthost. The dependable baseline is Mailgun on smtp.mailgun.org:587, SASL credentials in a root-only password map, STARTTLS certificate validation, and relay restrictions that reject unauthorized destinations. Validate the configuration, send a real message, and confirm both the queue and logs before putting the host into service.
What this setup does
Postfix normally can deliver mail directly to each recipient domain’s MX server. In a relay arrangement, it does not perform that final handoff itself. The relayhost setting sends remote messages to Mailgun’s SMTP service, where Mailgun authenticates the Ubuntu host and performs onward delivery.
The path is therefore:
- A local application submits a message to Postfix on the Ubuntu server.
- Postfix places the message in its queue and opens an SMTP connection to the configured Mailgun endpoint.
- Postfix authenticates with the SMTP username and password belonging to the Mailgun sending domain.
- Postfix negotiates TLS (STARTTLS on port 587) and transfers the message.
- Mailgun accepts the message for delivery and reports acceptance or a rejection that Postfix records in its logs.
This design avoids exposing application code to Internet delivery details, while still requiring you to protect credentials and prevent the server from becoming an open relay.
Prerequisites and decisions
Ubuntu host
- An Ubuntu server with
sudoaccess. - A resolvable hostname for the server. Set the system hostname and make sure local name resolution agrees with it before testing mail.
- Outbound TCP access from the server to the Mailgun submission port you choose.
Mailgun sending domain and credentials
Create or select the Mailgun sending domain that will appear in your messages. SMTP credentials are managed per domain. The password for the Mailgun control panel is not the password Postfix should use; retrieve the SMTP username and SMTP password shown for the sending domain instead.
#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: 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.
- Economical &Reusable: Built durable materials with a long-lasting battery,our CAGIWIRU air duster it's a sustainable alternative to disposable air cans.
Choose a submission port
| Port | Encryption behavior | When it fits | Important qualification |
|---|---|---|---|
| 587 | Plain SMTP connection upgraded with STARTTLS | Default choice for a Postfix smarthost | Mailgun recommends it when port 25 is blocked or throttled. |
| 2525 | Plain SMTP connection upgraded with STARTTLS | Alternative when firewall policy prevents 587 | Use the same authenticated-relay and certificate-validation safeguards. |
| 25 | Plain SMTP connection upgraded with STARTTLS | Only when your network permits normal outbound SMTP | More likely than submission ports to be blocked or throttled. |
| 465 | TLS starts immediately when the connection opens (implicit TLS) | Networks or applications that specifically require implicit TLS | Postfix must be configured for TLS wrapper mode; it is not the STARTTLS flow used on 587. |
Use port 587 in the commands below. If your firewall requires another endpoint, change the port consistently in both relayhost and the password-map key, then apply the matching TLS mode.
Install Postfix and select a smarthost configuration
- Update the package index and install Postfix:
sudo apt update
sudo apt install postfixUbuntu’s package configuration asks how this machine should send mail. Select the option described as an Internet smarthost, satellite system, or equivalent smarthost-oriented choice, depending on the Ubuntu release. The wording can differ, but the intent is the same: remote mail is handed to a specified SMTP server rather than delivered directly to recipient MX servers.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsWhen prompted for the system mail name, use the host’s fully qualified, resolvable hostname. You can revisit the package choices later by running sudo dpkg-reconfigure postfix, but manual edits to /etc/postfix/main.cf are still required for Mailgun authentication.
Ubuntu enables Postfix as a service. Do not assume that a successful package installation proves relay configuration is complete; the service can run while every remote message is deferred because authentication, TLS, or the relay endpoint is wrong.
Configure Postfix to use Mailgun
1. Set the relay and SMTP client security options
Edit /etc/postfix/main.cf and add or update the following parameters:
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.mailgun.org]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_security_level = may
smtp_tls_note_starttls_offer = yes
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crtThe square brackets in [smtp.mailgun.org]:587 are intentional. They tell Postfix to use that exact host and port instead of looking up the destination domain’s MX records. The same bracketed host and port must be used as the key in the password map.
smtp_sasl_auth_enable turns on authenticated SMTP. noanonymous prevents anonymous SASL mechanisms. The may TLS setting allows Postfix to attempt STARTTLS without making encryption mandatory; the stricter option is discussed below. Keep the CA-file setting pointed at the Ubuntu CA bundle installed on your release. If that path does not exist, install or repair the system CA certificates and use the bundle path provided by that Ubuntu installation.
Do not put a password directly in main.cf. Keeping credentials in a separate hash map limits accidental disclosure and is the format expected by the smtp_sasl_password_maps setting.
2. Create the SMTP password map
Create /etc/postfix/sasl_passwd as root. Its one-line entry must exactly match the relay host and port:
[smtp.mailgun.org]:587 SMTP_USERNAME:SMTP_PASSWORDReplace SMTP_USERNAME and SMTP_PASSWORD with the credentials for the Mailgun sending domain. Do not substitute the control-panel login. If you selected port 2525 or 25, use that port in both places; a mismatch causes authentication to fail even when the credentials themselves are correct.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
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.
Build the indexed database and lock down both files:
sudo postmap /etc/postfix/sasl_passwd
sudo chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
sudo chmod 600 /etc/postfix/sasl_passwdThe plaintext map contains a reusable secret. Keep it readable only by root, remove accidental copies from shell history and temporary directories, and check that backups do not make it world-readable. After changing the password, edit the plaintext map, run postmap again, and restart or reload Postfix so the new database is used.
Keep the server from becoming an open relay
A relayhost controls where Postfix sends mail; it does not, by itself, authorize arbitrary Internet users to submit mail through your server. The SMTP daemon must still reject destinations that are neither local nor authorized. Preserve your existing restrictions and ensure the effective recipient restrictions include the following pattern:
smtpd_recipient_restrictions =
permit_sasl_authenticated,
permit_mynetworks,
reject_unauth_destinationpermit_sasl_authenticated allows a client that has authenticated, and permit_mynetworks allows trusted local networks defined by Postfix. The final reject_unauth_destination is the critical guard: it rejects unauthenticated attempts to relay to arbitrary external domains. Do not replace it with a blanket permit rule. If your Ubuntu/Postfix version uses smtpd_relay_restrictions for this policy, apply the same allow-authenticated/allow-trusted/reject-unauthorized logic there and verify which parameter is active.
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Limit mynetworks to addresses you actually control. A broad private-network range can become an unintended relay if an untrusted system gains access to that network.
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.
Choose an appropriate TLS policy
Optional TLS: smtp_tls_security_level = may
The Mailgun example uses may. Postfix offers STARTTLS and authenticates when the server advertises it, but delivery can fall back if TLS negotiation fails. This can keep mail moving during a temporary TLS problem, but a fallback can expose SMTP credentials or message content on a hostile or misconfigured path. Treat this as a compatibility setting, not a guarantee that every hop from your server is encrypted.
Required TLS: smtp_tls_security_level = encrypt
After confirming the endpoint, CA bundle, system clock, and certificate validation, you can change the setting to encrypt. With required TLS, Postfix will not deliver when it cannot establish an encrypted session. Mailgun’s TLS policy documentation describes this as a deliberate fail-closed behavior: an unavailable or invalid TLS upgrade produces a delivery failure rather than plaintext fallback.
Port 465 and implicit TLS
Port 465 begins TLS immediately and therefore is not interchangeable with STARTTLS on 587, 25, or 2525. If you use it, configure Postfix’s SMTP client wrapper mode and an encryption-required policy, then validate the certificate before sending production mail. Do not merely change :587 to :465 while leaving the STARTTLS configuration unchanged.
Validate and restart Postfix
Run a syntax and file-permission check before restarting:
sudo postfix check
sudo systemctl restart postfix
sudo systemctl --no-pager --full status postfixpostfix check catches many malformed settings and missing files. A running service is not proof of a working relay, so continue with an authenticated message test and log inspection.
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.
Send a real test message
Test through the local submission path
Use the same local interface your application will use. For a simple command-line test, provide a recipient mailbox you control and a sender address authorized for the Mailgun sending domain:
printf 'Subject: Postfix Mailgun testnnThis is a relay test.n' | sendmail -v recipient@example.netReplace the example recipient with a real test address. The -v option prints the local submission and queueing result; Postfix then performs the remote SMTP transaction asynchronously.
Free tools Windows power users keep installed
One-click scans. No signup required.
Test Mailgun authentication directly with Swaks
A direct SMTP test separates Mailgun credentials and network reachability from local application behavior. Supply the SMTP username and password for the sending domain, not the control-panel password:
export SMTP_USERNAME='your-domain-smtp-username'
read -rsp 'Mailgun SMTP password: ' SMTP_PASSWORD; printf 'n'
swaks --server smtp.mailgun.org --port 587 --tls
--auth LOGIN
--auth-user "$SMTP_USERNAME"
--auth-password "$SMTP_PASSWORD"
--from 'sender@your-sending-domain.example'
--to 'recipient@example.net'
--header 'Subject: Mailgun SMTP test'
--body 'Authenticated STARTTLS test from Ubuntu.'Entering the password interactively avoids placing it literally in the command line. Clear the variables after the test and remember that shell history, process inspection, and diagnostic output can still disclose secrets if you paste them into commands.
Prove delivery with queue and log evidence
Immediately after submitting the message, inspect the queue:
mailqAn empty queue after a short interval usually means Postfix handed the message off; a persistent entry means delivery is deferred or failed. Review both the systemd journal and the traditional mail log because Ubuntu installations can use either or both:
sudo journalctl -u postfix -n 100 --no-pager
sudo tail -n 100 /var/log/mail.logFor a successful relay, look for SASL authentication followed by an accepted SMTP response from Mailgun. Also verify that the test message arrived at the recipient and that the sender address belongs to the configured sending domain. A local “queued” response alone does not prove remote acceptance.
Troubleshoot by symptom
| Symptom or log clue | Likely cause | What to check |
|---|---|---|
| Authentication failure or “SASL authentication failed” | Wrong per-domain credential, control-panel password, or map-key mismatch | Confirm the Mailgun SMTP username/password; verify the password-map key is exactly [smtp.mailgun.org]:587; rerun postmap after edits. |
| “No SASL mechanisms” or anonymous-authentication errors | SASL client support is missing or anonymous mechanisms are allowed | Check smtp_sasl_auth_enable = yes, smtp_sasl_security_options = noanonymous, and the installed Postfix package capabilities. |
| TLS handshake, certificate, or “cannot verify” errors | Missing CA bundle, incorrect hostname, wrong system clock, or a policy that requires TLS | Check the CA-file path, DNS resolution of smtp.mailgun.org, the server clock, and whether encrypt is being enforced before the endpoint is validated. |
| Connection timeout or “connection refused” | Outbound firewall filtering, blocked port, or a transient provider/network issue | Test the selected TCP port from the Ubuntu host, review egress firewall rules, and try 587 or 2525 when policy permits. Do not switch ports without changing the password-map key. |
| Message remains queued with repeated deferrals | DNS failure, blocked egress, provider limit, or a remote SMTP response | Read the exact status line in journalctl and /var/log/mail.log; investigate the named DNS, firewall, Mailgun-limit, or SMTP-response condition rather than deleting the queue blindly. |
| Unauthenticated external client can relay | Overly broad mynetworks or a permissive recipient restriction |
Restore reject_unauth_destination, narrow trusted networks, reload Postfix, and test from an unauthorized host. |
Operational safeguards after the first successful message
- Protect and rotate credentials. Treat
/etc/postfix/sasl_passwdand its database as secrets. When Mailgun credentials change, update the map, runpostmap, and reload or restart Postfix. - Monitor the queue. A growing queue can indicate an outage, an authentication regression, a blocked port, or a provider limit. Keep the original SMTP response when escalating the issue.
- Keep TLS validation enabled. Do not disable certificate checks simply to make a handshake succeed. Repair the CA bundle, hostname resolution, or clock instead.
- Restrict submission access. Allow local applications and only the networks that need to submit. Authentication and trusted-network rules should both be explicit.
- Protect configuration backups. Backups of
main.cfmay be harmless, but backups containingsasl_passwdare credential stores and require root-only access. - Retest after network changes. Firewall, DNS, hostname, and time-service changes can break SMTP even when no Postfix file changed.
Deployment checklist
- Ubuntu hostname resolves correctly and the server has sudo access.
- Mailgun sending domain is active and its SMTP credentials are available.
- Outbound access to the selected Mailgun port is allowed.
relayhostuses the bracketed host and the selected port.- SASL is enabled, anonymous mechanisms are disabled, and credentials are in
hash:/etc/postfix/sasl_passwd. - The password map is rebuilt with
postmapand readable only by root. - The Ubuntu CA bundle is present and its path is configured.
- TLS mode matches the selected port: STARTTLS for 587, 25, or 2525; implicit TLS for 465.
- Relay restrictions include authenticated/trusted permits followed by
reject_unauth_destination. postfix checkpasses, the service restarts cleanly, and status output is healthy.- A real test message is accepted by Mailgun and reaches the test mailbox.
- Queue and log output show no continuing deferrals or authentication errors.
Why this configuration is a sound default
Using Mailgun as the smarthost keeps Postfix’s role deliberately small: accept mail locally, authenticate to one provider endpoint, negotiate the required transport security, and report delivery status. Port 587 offers the broadest practical compatibility for this pattern because it uses STARTTLS and is less likely than port 25 to be blocked. The protected SASL map prevents credentials from being mixed into general configuration, while an explicit unauthorized-destination rejection prevents the Ubuntu host from relaying for strangers. Finally, a successful authenticated test plus queue and log evidence distinguishes a genuinely working relay from a service that merely starts without errors.
Quick Recap
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.
