Postfix mailq – send every x minutes

From the Postfix documentation, it appears you need to modify this section in your main.cf file:

http://www.postfix.org/ADDRESS_VERIFICATION_README.html

/etc/postfix/main.cf:
    smtpd_sender_restrictions = 
        permit_mynetworks
        ... 
        check_sender_access hash:/etc/postfix/sender_access
        reject_unknown_sender_domain
        warn_if_reject reject_unverified_sender 
        ...
    # Postfix 2.6 and later.
    # unverified_sender_reject_reason = Address verification failed

    # Default setting for Postfix 2.7 and later.
    # Note 1: Be sure to read the "Caching" section below!
    # Note 2: Avoid hash files here. Use btree instead.
    address_verify_map = btree:/var/lib/postfix/verify

This will put warning messages in your logs when a sender fails verification, but it won't reject it. You can remove the warn_if_reject line if you don't want to pollute your log files.

UPDATE:

If you want regular expressions, you'll need to compile PCRE support into Postfix (if it's not there already):

http://www.postfix.org/PCRE_README.html

Then, you can simply replace the line check_sender_access hash:/etc/postfix/sender_access with: check_sender_access pcre:/etc/postfix/sender_access and it will check for regex's in that file. If you're using Debian/Ubuntu, there's a package called postfix-pcre that will install support for PCRE.

http://www.postfix.org/pcre_table.5.html

Based on this thread on postfix mailing-list: different transport for all mail introduced via sendmail(1), looks like your case was possible. Unfortunately you can't only rely on two tables sender_dependent_relayhost_maps and smtp_sasl_password_maps. You need modify master.cf. The idea is using header_checks to route email to different transport. Then in each transport, we define smtp client that use independent credential and relayhost.

First define header_checks in main.cf and its pcre table

#main.cf
header_checks = pcre:/etc/postfix/header_dependent_relay

#/etc/postfix/header_dependent_relay

/^From:.*specialsender1\@example\.com/       smtp1:[host1.example.com]
/^From:.*specialsender2\@example\.com/       smtp2:[host2.example.com]
/^From:.*specialsender3\@example\.com/       smtp3:[host3.example.com]

Good, now we setup smtp1,smtp2,smtp3 transport in master.cf

#master.cf
smtp1    unix  -       -       -       -       10       smtp
    -o smtp_sasl_password_maps=hash:/etc/postfix/smtp1.relay
smtp2    unix  -       -       -       -       10       smtp
    -o smtp_sasl_password_maps=hash:/etc/postfix/smtp2.relay
smtp3    unix  -       -       -       -       10       smtp
    -o smtp_sasl_password_maps=hash:/etc/postfix/smtp3.relay

File smtpX.relay has similar content e.g.

[hostX.example.com]   userX:passwordX

Disclaimer:

• The hash table of smtp_sasl_password_maps is only for example. You can replace it with mysql table.
• You can also replace pcre table of header_checks with combination of SELECT and REGEXP in MySQL . But it may kill your database as postfix will hit MySQL for every header line