Help needed with 2 mail.log errors I don't understand.

I am sorry to trouble you. I need a little bit of guidance regarding sending mail on my server. I'm getting errors that I'm not quite sure what they mean.

  1. What exactly is this error in the mail.log telling me? Is it telling me that there is an error in the FROM email or the Reply to email? (In other words MY EMAIL?)

Feb 4 19:56:40 rhodesia02 postfix/smtp[17620]: AB4433CD91:,[2c0f:fd58:101f:1501::102]:25, delay=2.1, delays=0.01/0/1.8/0.21, dsn=4.5.2, status=undeliverable (host[2c0f:fd58:101f:1501::102] said: 452 4.5.2 Could not resolve sender domain. (in reply to MAIL FROM command))

  1. I'm trying to run tests to check if the to emails I am sending are valid. I'm doing this:
    sendmail -bv

It tells me: Mail Delivery Status Report will be mailed to <root>.
I tried to find the root log but I can't see it. </root>

I would appreciate some guidance please.


2 Replies

The DNS resolution error you mentioned could be from the recipient's end, but it's more likely caused by DNS configuration issues.

While there may be some variation to this depending on your setup and specific needs, in general you'll want to start by setting up A/AAAA and rDNS records.

Our guides on configuring DNS and rDNS records within the Linode Manager:

Once your DNS configuration is complete, you can confirm that these records have been configured correctly by running the following commands:

# for checking the A record
dig +short $Domain

# for checking rDNS
dig -x $IPaddress +short 

We also recommend creating an SPF record for your mailing domain as this will help improve email deliverability. For more information, please see our Running a Mail Server guide:

Finally, you may also need to set up other records depending on your use case. For example, in our guide to Configuring an Email Server with Postfix, Dovecot, and MySQL on Debian and Ubuntu, we specifically point to setting up MX records. This post on our Community Site covers many possibile deliverability issues including those caused by DNS records:

To get the information from the Mail Delivery Status Report, this post recommends checking the email for the root user and explains how to find that information.

On that same forum, there is a response explaining how to send the report to a specific mailbox that could be useful moving forward.

Thank you very much for your answer. It's much appreciated.


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