Postfix multi instance transport

postfix

I'm configuring a postfix mailing server with multiple instances.
Each instance has been assigned it's own ip and domain.
For some of the instances, I've enabled rate delays for specific domains:

main.cf

yahoo_destination_rate_delay = 5s
yahoo_concurrency_failed_cohort_limit = 10
yahoo_destination_concurrency_limit = 10
ymail_destination_rate_delay = 5s
ymail_concurrency_failed_cohort_limit = 10
ymail_destination_concurrency_limit = 10

master.cf

yahoo      unix  -       -       n       -       -       smtp
    -o syslog_name=postfix-3
    -o smtp_fallback_relay=
ymail      unix  -       -       n       -       -       smtp
    -o syslog_name=postfix-3
    -o smtp_fallback_relay=

transport

yahoo.com    yahoo:
ymail.com    ymail:

My question is, how does each instance know which transport to use? i set

postmap /etc/postfix-3/transport

but is that enough?

It seems to be working but that could only be because a few other instances have similar transports. I'm afraid each instance could be reading an incorrect transport map. Should I assign each instance a specific transport file or is that assumed?

Thanks!

Best Answer

I don't know what you mean. Each instance has it's own folder under /etc/ and you have transports configured in each master.cf in each instance folder.

All instances are independent of each other and don't know each others configuration. Except the few configuration parameters that configure the instances itself.

Related Solutions

Postfix – Fixing Mail Loops Back to Myself Issue

This happens when domain.com has an MX record (or, in the absence of an MX, an A record) that points to your Postfix server, but your Postfix server is not configured to accept mail for that domain. It's commonly seen in two situations:

You've acquired a new domain that you want to use for email, but you just forgot to add it to Postfix. There are a couple ways to do it. In my case, I'm using the virtual table to map addresses to real local users, so I list my domains in the virtual_alias_domains directive in main.cf.
The domain has its MX record set to a host that resolves to 127.0.0.1. Some malware will use this trick so they can set their return address to a valid domain, which most anti-spam measures will check for. However, the MX effectively prevents any delivery to that address, so the sender doesn't have to deal with replies or bounces.

Postfix – Specifying an Instance to Send Outbound Email

When you send email via local submission a.k.a sendmail it will use default instance e.g. red.example.com. This behavior was explained in postfix official documentation.

One Postfix instance is special: this is the instance whose configuration directory is the default one compiled into the Postfix utilities. The location of the default configuration directory is typically /etc/postfix, and can be queried via the "postconf -d config_directory" command. We call the instance with this configuration directory the "default instance".

The default instance is responsible for local mail submission. The setgid postdrop(1) utility is used by the sendmail(1) local submission program to spool messages into the maildrop sub-directory of the queue directory of the default instance.

Even in the rare case when "sendmail -C" is used to submit local mail into a non-default Postfix instance, for security reasons, postdrop(1) will consult the default main.cf file to check the validity of the requested non-default configuration directory.

So, while in most other respects, all instances are equal, the default instance is "more equal than others". You may choose to create additional instances, but you must have at least the default instance, with its configuration directory in the default compiled-in location.

Some suggestions:

Based on above snippet, you could try to use sendmail -C to specify the instance to submit email. Or
The other workaround is swap the the instance, e.g. red.example.com become blue.example.us and vice versa.

Edit based on comments below

sendmail: fatal: User account5(###) is not allowed to submit mail

The error above caused by authorized_submit_users parameter is blank (postfix-blue instance). The effect is nobody could execute sendmail via postfix-blue instance. Adding account5 to that parameter should solves the problem.

Another error

warning: connect to transport private/smtp: Connection refused

was caused by missing smtp transport in master.cf. Make sure this line present in master.cf

smtp      unix  -       -       n       -       -       smtp

and add -o smtp_bind_address=192.168.36.51 at the end of the line so email will send through address 192.168.36.51.

Best Answer

Related Solutions

Postfix – Fixing Mail Loops Back to Myself Issue

Postfix – Specifying an Instance to Send Outbound Email

Edit based on comments below

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