Resolved Reducing Postfix "Concurrent Connections" Problem

[tetrahall]

Server operating system version

Centos 7.7

Plesk version and microupdate number

Plesk Obsidian 18.0.74.3

Hello,

I'm trying to reduce the "Concurrent Connections" for sending hotmail/outlook emaails.

The default value is 20. Hotmail requires a value of 3.

So, I;ve added certain lines at *the end* of the following files in postfix.

master.cf
hotmail-throttle unix - - n - 3 smtp
-o syslog_name=postfix-hotmail
-o smtp_destination_rate_delay=1s
-o smtp_destination_concurrency_limit=3

transport
hotmail.com hotmail-throttle:
outlook.com hotmail-throttle:
live.com hotmail-throttle:
msn.com hotmail-throttle:

main.cf
transport_maps = hash:/etc/postfix/transport

When either of the the following commands are run
# postmap /etc/postfix/transport
# postfix reload

This message is displayed"

postmap: warning: /etc/postfix/main.cf, line 735: overriding earlier entry: transport_maps=, hash:/var/spool/postfix/plesk/transport

line 735:
This is the line I added at the bottom of the file "main.cf"
transport_maps = hash:/etc/postfix/transport

What am I doing wrong, please?

 

[scsa20]

Sounds like your main.cf already has a transport_maps defined. Just delete the line you've made, locate the one that plesk defined already, and add it yours with a comma so it'll look something like this:

transport_maps = hash:/var/spool/postfix/plesk/transport, hash:/etc/postfix/transport

 

[tetrahall]

scsa20,
Thank you. The error message has disappeared.

However, to displays all limits, I run this command:
# postconf | grep concurrency_limit

it yields several lines...
default_destination_concurrency_limit = 20

hotmail-throttle_destination_concurrency_limit = $default_destination_concurrency_limit

Shouldn't hotmail-throttle_destination_concurrency_limit = 3?

 

[tetrahall]

Also, the following command should display customized (non-default) concurrency settings in main.cf file

#postconf -n | grep concurrency

But it doesn't display anything!

 

[scsa20]

Honestly the best way to test to see if it worked is to simply do a test while tailing the maillog

tail -f /var/log/maillog

And look for the transport. Here's an example of mine when I set it up just now:

Jan 25 22:34:44 akheera dovecot[]: service=imap, [email protected], ip=[::1]. Disconnected: Logged out rcvd=1162, sent=1885
Jan 25 22:34:44 akheera postfix/smtp[]: DDC: to=<@gmail.com>, relay=gmail-smtp-in.l.google.com[64.233.180.26]:25, delay=1.2, delays=0.23/0.01/0.36/0.58, dsn=2.0.0, status=sent (250 2.0.0 OK  17 -502fc024772si79214681cf.36 - gsmtp)
Jan 25 22:34:46 akheera postfix-hotmail/smtp[]: DDC: to=<@hotmail.com>, relay=hotmail-com.olc.protection.outlook.com[52.101.68.2]:25, delay=3, delays=0.23/0.01/0.65/2.1, dsn=2.6.0, status=sent (250 2.6.0 <acb--7-78c6a900@17646742> [InternalId=, Hostname=DM6PR13MB3772.namprd13.prod.outlook.com] 11446 bytes in 0.306, 36.452 KB/sec Queued mail for delivery -> 250 2.1.5)

As you can see the one sent to gmail used the normal postfix/smtp transport while the one sent to hotmail used the postfix-hotmail/smtp transport.

 

[tetrahall]

Thanks, I will try that.

 

[tetrahall]

Sorry, it doesn't work for me.

Every source on google just mentions the steps I outlined in the first post.

This command:
# postconf | grep concurrency_limit

still yields:
hotmail-throttle_destination_concurrency_limit = $default_destination_concurrency_limit

Could the answer lie in this command?
postmap /etc/postfix/transport

Is there a need to attach main.cf, master.cf or transport ?

 

[tetrahall]

Another indication that it hasn't worked is that the mail log still states hotmail/outlook "Concurrent Connections" problem.

 

[Sebahat.hadzhi]

Can you please confirm what you get when you execute:

postconf -M | grep hotmail

Also, an example error from the mail log? Thanks in advance.

 

[tetrahall]

Sebahat.hadzhi,

Many thanks for your reply. Actually, after my previous message, I contacted support of our hosting company seeking their advice. They suggested, as a first step, to "reboot" the server and flush the mail queue with the command "postqueue -f".

This has worked. No more hotmail/outlook error messages in the mail log.

Thank you for suggesting this:
postconf -M | grep hotmail

I will celebrate. The result is:

hotmail-throttle unix - - n - 3 smtp -o syslog_name=postfix-hotmail -o smtp_destination_rate_delay=1s -o smtp_destination_concurrency_limit=3

The question remains: why is it that the following command
postconf | grep concurrency_limit
still displays nothing ?!

I will leave it at that. The issue has been resolved, thanks to you and to scsa20 for your help