Incoming mail bounce back with "Too many hops" message.

[archawan]

I have one static IP, with one server running Proxmox VE.

I have installed Virtualmin for mail server and Proxmox Mail Gateway.

I forwarded the port 25 to PMG. I created a transport map in postfix to PMG.

Outgoing mails are fine. Incoming mails are getting bounced back.

Error:

<someone@example.com>: host 192.168.0.142[192.168.0.142] said:
554 5.4.0 Error: too many hops (in reply to end of DATA command)

Mail.log
"Jun 24 11:50:07 hostname postfix/smtp[27951]: warning: 192.168.0.142:26: dane configured with dnssec lookups disabled
Jun 24 11:50:07 hostname postfix/smtp[27951]: 33DB449C12E3: to=<other@other.com>, relay=192.168.0.142[192.168.0.142]:26, delay=0.15, delays=0.11/0.01/0.01/0.03, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 5154380016)
Jun 24 11:52:17 hostname postfix/smtpd[29624]: connect from unknown[192.168.0.142]
Jun 24 11:52:17 hostname postfix/smtpd[29624]: DAC8649C0DF9: client=unknown[192.168.0.142]
Jun 24 11:52:17 hostname postfix/smtpd[29624]: disconnect from unknown[192.168.0.142] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Jun 24 11:52:17 hostname postfix/smtp[29636]: warning: 192.168.0.142:26: dane configured with dnssec lookups disabled
Jun 24 11:52:17 hostname postfix/smtp[29636]: DAC8649C0DF9: to=<other@other.com>, orig_to=<other@other.com>, relay=192.168.0.142[192.168.0.142]:26, delay=0.1, delays=0.06/0.01/0.01/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as E98EC80012)
Jun 24 11:52:18 hostname postfix/smtpd[29624]: connect from unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: 1C67649C0DF9: client=unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: disconnect from unknown[192.168.0.142] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Jun 24 11:52:18 hostname postfix/smtp[29636]: warning: 192.168.0.142:26: dane configured with dnssec lookups disabled
Jun 24 11:52:18 hostname postfix/smtp[29636]: 1C67649C0DF9: to=<other@other.com>, relay=192.168.0.142[192.168.0.142]:26, delay=0.09, delays=0.06/0/0.01/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 2A03880012)
Jun 24 11:52:18 hostname postfix/smtpd[29624]: connect from unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: 3D79C49C0DF9: client=unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: disconnect from unknown[192.168.0.142] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Jun 24 11:52:18 hostname postfix/smtp[29636]: warning: 192.168.0.142:26: dane configured with dnssec lookups disabled
Jun 24 11:52:18 hostname postfix/smtp[29636]: 3D79C49C0DF9: to=<other@other.com>, relay=192.168.0.142[192.168.0.142]:26, delay=0.08, delays=0.05/0/0.01/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 47ED980012)
Jun 24 11:52:18 hostname postfix/smtpd[29624]: connect from unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: 5C1AB49C0DF9: client=unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: disconnect from unknown[192.168.0.142] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Jun 24 11:52:18 hostname postfix/smtp[29636]: warning: 192.168.0.142:26: dane configured with dnssec lookups disabled
Jun 24 11:52:18 hostname postfix/smtp[29636]: 5C1AB49C0DF9: to=<other@other.com>, relay=192.168.0.142[192.168.0.142]:26, delay=0.04, delays=0.02/0/0.01/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 5EF5D80012)
Jun 24 11:52:18 hostname postfix/smtpd[29624]: connect from unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: 7243549C0DF9: client=unknown[192.168.0.142]
Jun 24 11:52:18 hostname postfix/smtpd[29624]: disconnect from unknown[192.168.0.142] ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5"

This keeps going on. I have filtered out mail.log to only the PMG ip address. I am receiving a lot of spam mails and brute force attack attempts, thus want to shift to PMG.

Please help me out. Thanks.

Edit: Redacted the hostname and mail ids.

 

[archawan]

Does anyone know how to solve this?

 

[mira]

Please provide such a bounce mail as .eml file. It could be you've configured a loop.

 

[archawan]

Please provide such a bounce mail as .eml file. It could be you've configured a loop.

 

[mira]

Is 192.168.0.21 your mail server? And you do have a loop:
PMG (192.168.0.142) sends to PMG (localhost) which sends to 192.168.0.21 which then again sends to PMG (192.168.0.142).

 

[archawan]

Is 192.168.0.21 your mail server?

Yes

 

[archawan]

Is 192.168.0.21 your mail server? And you do have a loop:
PMG (192.168.0.142) sends to PMG (localhost) which sends to 192.168.0.21 which then again sends to PMG (192.168.0.142).

How can I solve that?

 

[archawan]

I have done this:
From internet to PMG : Port 25
From PMG to internet : Port 25
And in postfix mail server, a transport layer has been configured as
* smtp:192.168.0.142:26
And in Virtualmin I have allowed port 26 in firewalld.