Question Reverse DNS is not a valid Hostname (crazy...)

[Tomas.Michal]

Server operating system version

Ubuntu 22.04.4 LTS

Plesk version and microupdate number

18.0.62

Hello,
i have follow error on my MailServer, but all mails can be sending to other in success.

If I Check

Network Tools: DNS,IP,Email

DNS and Network troubleshooting and diagnostic tools integrated into one sweet interface.

mxtoolbox.com

Then the SMTP Valid Hostname Fail to Reverse DNS is not a valid Hostname

The PTR Check on :

PTR Record Lookup - Check Reverse DNS (PTR) records for any domain

Instant DNS Lookup. Check DNS records and propagation globally.

www.whatsmydns.net

Looks very good:
id 37234, opcode QUERY, rcode NOERROR, flags QR RD RA
;QUESTION
61.104.132.212.in-addr.arpa. IN PTR
;ANSWER
61.104.132.212.in-addr.arpa. 792 IN PTR tompaz.org.
;AUTHORITY
;ADDITIONAL

My Reverse DNS is st to tompaz.org.
In my postfix Konfiguration i set the myhostname = mail.tompaz.org.

My server are provided by strato and i use Ubuntu 22.04.4 LTS with
Plesk Obsidian Version 18.0.62

Crazy is my /etc/hosts (after reboot) set strato (cloud.cfg) is overwirtten by:

127.0.1.1 ip212-132-104-61.pbiaas.com ip212-132-104-61
127.0.0.1 localhost
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Any hints ?? ...

Tomas

 

[ChristophRo]

PTR should either be set to mail.tompaz.org or the postfix myhostname to "tompaz.org"
Just make sure the HELO and the PTR do match up exactly, or you will run into problems when sending emails to certain destinations.

The hosts file looks OK and does not need any changes

 

[Kaspar@Plesk]

Note that mxtoolbox.com will complain when using a 2nd level domain (like example.com) instead of a 3rd level domain (like host.example.com) as the hostname. You can safely ignore the mxtoolbox.com warning. A 2nd level domain is just as valid.

 

[Tomas.Michal]

Hello,
thanks for the quick reply.
Unfortunately, my problem is probably a bit more difficult.

In /etc/postfix/main.cf I had to reset the setting to original:

myhostname = ip212-132-104-61.pbiaas.com

The reason for this is that mails to invalid names are not returned.
([email protected]) / Undelivered Mail Returned to Sender

I cannot set the reverse DNS for my IP address to the domain ip212-132-104-61.pbiaas.com. I can only use a domain that I have purchased (e.g. tompaz.org).
at the moment my config looks like this:

Connecting to 212.132.104.61

220 ip212-132-104-61.pbiaas.com ESMTP Postfix (Ubuntu) [313 ms]
EHLO keeper-us-east-1d.mxtoolbox.com
250-ip212-132-104-61.pbiaas.com
250-PIPELINING
250-SIZE 24576000
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-DSN
250 CHUNKING [231 ms]
MAIL FROM:<[email protected]>
250 2.1.0 Ok [231 ms]
RCPT TO:<[email protected]>
454 4.7.1 <[email protected]>: Relay access denied [297 ms]

LookupServer 2337ms

The PTR Lookup looks fine:
id 33480, opcode QUERY, rcode NOERROR, flags QR RD RA
;QUESTION
61.104.132.212.in-addr.arpa. IN PTR
;ANSWER
61.104.132.212.in-addr.arpa. 7200 IN PTR tompaz.org.
;AUTHORITY
;ADDITIONAL

I don't know how to tackle the problem yet, maybe the provider has to set the reverse dns to ip212-132-104-61.pbiaas.com ?

Tomas

 

[Tomas.Michal]

Note that mxtoolbox.com will complain when using a 2nd level domain (like example.com) instead of a 3rd level domain (like host.example.com) as the hostname. You can safely ignore the mxtoolbox.com warning. A 2nd level domain is just as valid.

OK.. thank you Kaspar...