Resolved Reverse DNS does not match SMTP Banner

[JohnBee]

It would appear that I have this problem on my Plesk server, and I can't figure out what's causing it.
I recently tried replying to an email and got a message saying my email was rejected - I assume this is the cause

With that said, could someone help me troubleshoot and fix this?

 

[Martin Dias]

SMTP Banner is normally the hostname, and it should be a FQDN in an best case scenario.
Reverse DNS needs to be set normally over the Server Providers Panel or Support

You can check the SMTP Banner with:

# telnet localhost 25

Here as an example:

root@mail ~ # telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain.
Escape character is '^]'.
220 mail.example.com ESMTP Postfix
quit
221 2.0.0 Bye
Connection closed by foreign host.

Here the Banner is mail.example.com

The hostname can be changed over Tools & Settings > Server Settings and over CLI

# hosnamectl set-hostname mail.example.com

the PTR/Reverse DNS can be checked with:

# host <IP>

Here as an example:

root@mail ~ # host 203.0.113.2
2.113.0.203.in-addr.arpa domain name pointer mail.example.com.

 

[JohnBee]

Hi and thanks so much for helping out with this.
I ran the tests and found the following;

# telnet localhost 25

Connected to localhost.localdomain.
Escape character is '^]'.
220 webshot-5eb7aafc891d2.local ESMTP Postfix

I then looked in Tools & Settings, and found that hostname was indeed properly set with my.hostname.net
I then ran the following command:

# hosnamectl set-hostname my.hostname.net

Then verified with the following:
# host <my IP>

And receive the following response
157.136.141.99.in-addr.arpa domain name pointer my.hostname.net.

With that said, it would appear that my Postfix banner is reporting the webhost hostname rather than the set hostname
Any idea what could cause this, or how I might fix it?

 

[JohnBee]

Just to update, I followed the following Plesk article and resolved the issue;

How to change the hostname and SMTP banner in Postfix on a Plesk server

Applicable to: Plesk for Linux Question How to change the hostname in Postfix on a Plesk server? How to change the SMTP banner in Postfix on a Plesk server? Answer Connect to a Plesk ser...

support.plesk.com

Thanks for the help

 

[fmaz008]

My SMTP banner is:
220 mydomain.ca ESMTP Postfix

Is the suggestion really to change the whole server hostname to mail.mydomain.ca ?

Wouldn't the hostname applies to more than just the mail server ?

 

[Ddungu]

SMTP Banner is normally the hostname, and it should be a FQDN in an best case scenario.
Reverse DNS needs to be set normally over the Server Providers Panel or Support

You can check the SMTP Banner with:

# telnet localhost 25

Here as an example:

root@mail ~ # telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain.
Escape character is '^]'.
220 mail.example.com ESMTP Postfix
quit
221 2.0.0 Bye
Connection closed by foreign host.

Here the Banner is mail.example.com

The hostname can be changed over Tools & Settings > Server Settings and over CLI

# hosnamectl set-hostname mail.example.com

the PTR/Reverse DNS can be checked with:

# host <IP>

Here as an example:

root@mail ~ # host 203.0.113.2
2.113.0.203.in-addr.arpa domain name pointer mail.example.com.

In my case, I have two records of PTR. Is it okay.

 

[Peter Debik]

The PTR record for a reverse name is expected to resolve to the canonical name of that ip address. That is said 1 name. Why would you want to have multiple PTR records?