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Postfix is mail transfer agent (MTA) software: it accepts and routes email using SMTP, then hands messages to configured delivery services. It can support a self-managed mail system, but it is not a complete hosted-mail product. Its behavior depends on the Postfix version, configuration, operating-system packaging, and the services around it.
What Postfix does
Postfix handles the transfer and routing layer of email. It can receive messages over SMTP, queue them while delivery is pending, and deliver or relay them according to its configuration. Administrators use it for tasks such as sending outbound mail from systems, relaying mail, and accepting mail for domains they operate.
A working mail service involves more than the MTA. Postfix does not by itself provide a complete hosted mailbox product or guarantee secure, reliable delivery. A self-managed deployment also requires appropriate DNS, mailbox or delivery arrangements, security controls, ongoing patching, and attention to deliverability. The official Postfix documentation is the starting point for version-specific administration.
Check the release and maintenance status
As of September 7, 2026, the official Postfix announcements page lists 3.11.7 as the stable release. It also lists updates for legacy branches, but a listed update does not mean every branch remains supported or has received every relevant fix. Check the official announcements and the package information from your operating-system vendor before installing or upgrading; distribution packages can lag upstream or carry vendor-specific changes.
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The 3.11.7 announcement describes medium-impact issues, including problems that can enable remote denial of service and local memory corruption or policy bypass. It says supported releases 3.8–3.11 receive updates and cautions that out-of-support branches 3.5–3.7 omit some earlier patches. Administrators on older installations should review applicable advisories and vendor patch status rather than assuming that the newest update listed for an old branch addresses everything.
How to configure Postfix TLS
Postfix TLS settings govern encryption between mail systems during a connection. They do not provide end-to-end message encryption: messages may be stored or relayed in places where that connection-level protection does not apply. The effective behavior is influenced by the Postfix version and compatibility_level, so do not infer a host’s policy solely from its version number.
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Understand the default before changing it
For Postfix 3.11 and later, when compatibility_level is 3.11 or higher and the build includes TLS support, the SMTP client default for smtp_tls_security_level is may. With older compatibility levels, the default may be empty, which means TLS is not used unless other settings enable it. Confirm the effective configuration and consult the TLS documentation for the installed version before relying on a presumed default.
Choose opportunistic or mandatory TLS deliberately
| Policy | What it means | Operational trade-off |
|---|---|---|
Opportunistic (may) |
Postfix attempts TLS when the destination supports it. | Delivery may proceed without encryption if TLS is unavailable or cannot be used, so this does not guarantee an encrypted connection. |
Mandatory (encrypt) |
Postfix requires TLS for the applicable delivery. | Messages can be deferred when a destination cannot meet the requirement. This can impair interoperability with destinations that do not support the required TLS policy. |
The Postfix TLS guide states that “mandatory TLS encryption is not viable as a default security level for mail delivery to the public Internet.” A mandatory policy can make sense for a defined set of destinations with known TLS capabilities, but it is not a general substitute for opportunistic encryption across arbitrary Internet mail.
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Encryption and peer verification are separate questions. Whether a TLS connection is authenticated depends on the configured policy and verification behavior; merely enabling TLS does not establish that the peer identity has been verified. Use the configuration reference for the installed release to choose and validate the policy appropriate to the SMTP client or server role.
How Postfix delivers mail for virtual domains
Postfix’s virtual(8) delivery agent is designed for virtual mail hosting. It looks up the full recipient address in configured maps rather than relying only on the recipient name of a local Unix account. This allows recipient-to-mailbox mapping to be managed independently of local account names.
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Local delivery and virtual delivery therefore differ in their recipient lookup model: local delivery is associated with local system accounts, while virtual delivery uses address-based mappings. The virtual(8) manual describes the virtual agent’s delivery role. Forwarding and out-of-office behavior are separate functions; for example, virtual alias maps can provide address forwarding, but they are not the same thing as the virtual delivery agent itself.
The exact maps, mailbox locations, and supporting services depend on the deployment. The manual describes the mechanism, not a universal setup recipe for every operating system or map backend, so follow documentation matching your installed Postfix version and environment.
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Postfix or a hosted mail service?
Postfix is a fit when you need to administer SMTP transfer and delivery behavior yourself and can maintain the surrounding mail infrastructure. A hosted mail service may be more appropriate when you want someone else to operate the mail platform. This is a scope distinction, not a feature-for-feature comparison: no particular provider or hosted service is established here.
If you choose to self-host Postfix on a VPS, the VPS supplies computing infrastructure, not a finished mail service. You remain responsible for DNS, deliverability, patching, configuration, and mail-server security.
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