Table of Contents for

Postfix: The Definitive Guide

Postfix reports this error when a DNS reply points to your mail server, but Postfix has not been configured to accept mail for the domain. Postfix accepts mail for domains listed in mydestination, relay_domains, virtual_mailbox_domains, virtual_alias_domains, and domains that resolve to IP addresses listed in inet_interfaces and proxy_interfaces. Your domain must be listed in one of these parameters.

It depends on the type of file you are changing. Changes in files that Postfix reads into memory at startup require a reload. Examples of such files are main.cf, master.cf, and any lookup table using regular expressions. DB or DBM files are not read into memory and don’t require reloading Postfix when they are changed.

No. Most administrators with complex configurations create a Makefile that will cat the necessary files together. If you have other regular administrative tasks, add them to your Makefile too. Your Makefile should have an entry that looks something like this:

main.cf: file1 file2 file3
        cat file1 file2 file3 > main.cf.new
        mv main.cf.new main.cf

Then type make main.cf to rebuild your configuration file.

This is not currently available in Postfix.

By design this is not implemented in Postfix directly. It’s not the job of an MTA, and it’s not as simple a problem as it seems because of MIME and digital signatures. MIME messages have a structure that can be very complex. Digital signatures attest to the fact that a signed message has not been modified. Adding a footer to the bottom of a message breaks both of these. Some people add short text to the headers of email messages, but the text is not likely to be seen by most users. The real solution is to configure your clients to add whatever text is required.

Specify an address in the always_bcc parameter. It will receive copies of all messages.

This is not really a function of Postfix, although you may achieve what you’re looking for with the mailbox_size_limit. Be aware that if you use maildir-style mailboxes, this parameter limits only the size of individual mail files and not the size of the entire mailbox. Mailbox quotas are best enforced by the mail store itself, which might be done through normal operating system accounting or your POP/IMAP server configuration.

The idea behind this message is that users should contact their own postmasters for assistance, since the local postmaster is quite possibly the one who has to deal with the problem. If you definitely want to make the change, you have to modify the source code.

If you are using an external program for delivery, it might not handle more than one address at a time. Such is the case with maildrop, for example. To make sure that Postfix passes messages for delivery one at a time, set the transport _destination_recipient_limit parameter in main.cf to 1. transport is the name of the transport method making the deliveries. If you are using maildrop, the parameter looks like the following:

maildrop_destination_recipient_limit = 1

Specify the IP address of the interface you want Postfix to use in the inet_interfaces parameter.

This is controlled by the delay_warning_time parameter. By default it’s set to 0 for “never”.

Postfix does not support EXPN. Because of Postfix’s architecture and concern for security, the unprivileged SMTP server doesn’t know anything about local aliases. It’s the privileged local delivery agent that actually expands aliases at the point of delivery. If you use a mailing-list manager, it most likely has a command to tell you who is on the list, or you may have to check the aliases file on the mail server system.

The mailbox_transport parameter is set to a service from master.cf, while mailbox_command refers to an actual command on the mail server filesystem. There are a few parameters that can affect mailbox delivery. The parameters in order of preference are mailbox_transport, mailbox_command_maps, mailbox_command, and home_mailbox.

Add header checks that match the header lines showing your internal systems and specify the IGNORE action for them.

You can specify an address in the luser_relay parameter and disable local_recipient_maps:

luser_relay = info
local_recipient_maps =

Be careful if you do this. With the prevalence of spam, the address you specify is liable to catch a large amount of junk mail.

You probably have soft_bounce turned on.

# postsuper -d ALL

Note that the word ALL must be all capital letters, and that executing this command deletes all of the mail in your queue.

Postfix logs messages to your system’s syslogd daemon. Check your system documentation to find the actual log file.

It’s normal if you have:

disable_dns_lookups = yes

specified in main.cf. You might also have a transport map specified in brackets, in which case Postfix delivers directly to the system:

example.com     smtp:[mail.example.com]

You don’t want to block messages based on the fact that they have a null return path. Accepting null envelope addresses is required by the standards. The technique is used to prevent looping of error notifications. You’ll have to identify the spam by some other means.

No. Header and body checks are applied to every message and should be used for simple checks that can easily be applied to all mail. If you need anything more sophisticated, you should set up a content filter that has the smarts you need.