550 sender rejected – sender domain has no MX/A record. Different IP for MX & A Records

Stephanus Yanaputra asked:

I have a website that has different hosting for website and email. I host the website and another company hosts the email and handle the domain.

This is how the domain is set up: (The domain name & IP are masked for privacy purpose)

Record                  Type    TTL     Content
<domain>.com.au         A       1 hour  180.235.xxx.xx
<domain>.com.au         MX      1 hour  mail.<domain>.com.au
<domain>.com.au         A       1 hour  125.255.xx.xx
<domain>.com.au         NS      1 hour  ns1.planetdomain.com
<domain>.com.au         NS      1 hour  ns2.planetdomain.com
<domain>.com.au         SOA     1 hour  ....
blog.<domain>.com.au    A       1 hour  180.235.xxx.xx
www.<domain>.com.au     A       1 hour  180.235.xxx.xx

The website uses WordPress and occassionaly send enquiries to the company. However there are times that this error message will come up:

host mx1.pm.telstra.com []
SMTP error from remote mail server after MAIL FROM:<spurling@vps1.preschem.com> SIZE=2300:
550 5.1.0 <spurling@vps1.preschem.com> sender rejected - sender domain has no MX/A record

I understand that the MX records are pointing to different IP Address. I don’t know how, but WordPress seems to be able to send email just fine despite having different IP Address for the MX Records. However for some addresses, the emails keep bouncing back.

How do I fix this issue? Do I have to fix this from the webhosting side or from domain side?

I have set the MX Entries in cPanel as Remote Mail Exchanger. So emails will go to the email hosting instead.

My answer:

The message is quite right: Your sender’s domain hasn’t got either an MX or A record.

$ host vps1.preschem.com
Host vps1.preschem.com not found: 3(NXDOMAIN)

According to RFC 5321 section 2.3.5 the sender domain must be valid and resolvable. If not, any mail server can reject the mail.

You fix the issue by giving it an appropriate address record or records.

View the full question and answer on Server Fault.

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