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On my server, sendmail was taking 60s to send a simple message. After some googling, I found out that it was due to a DNS problem. I had this log:

Sep 13 08:00:01 myserver sm-msp-queue[1493]: My unqualified host name (myserver) unknown; sleeping for retry
Sep 13 08:01:01 myserver sm-msp-queue[1493]: unable to qualify my own domain name (myserver) -- using short name

The solution was to edit /etc/hosts and add names with a dot at the end

127.0.0.1 localhost locahost.
127.0.0.1 myserver myserver.

Now sendmail runs very quickly, but the messages as not delivered anymore. I'm sending just a "hello" to my gmail account.

echo "hello" | sendmail -v "xxx@gmail.com"

I've seen some people saying that the remote server may reject messages, but I don't understand, because they were being delivered before altering the hosts file. I don't want to host a mail server. I just need to send messages to myself. Here's the output from the command line above:

220 myserver. ESMTP Sendmail 8.14.4/8.14.4/Debian-4.1ubuntu1; Fri, 18 Sep 2015 13:50:45 -0300; (No UCE/UBE) logging access from: localhost(OK)-localhost [127.0.0.1]
>>> EHLO myserver.
250-myserver. Hello localhost [127.0.0.1], pleased to meet you
...
250 2.0.0 Verbose mode
>>> MAIL From:<www-data@myserver> SIZE=3 AUTH=www-data@myserver
250 2.1.0 <www-data@myserver>... Sender ok
>>> RCPT To:<xxx@gmail.com>
>>> DATA
553 5.1.8 <xxx@gmail.com>... Domain of sender address www-data@myserver does not exist
503 5.0.0 Need RCPT (recipient)
>>> RSET
250 2.0.0 Reset state
>>> RSET
250 2.0.0 Reset state
www-data@myserver... Using cached ESMTP connection to [127.0.0.1] via relay...
>>> MAIL From:<> SIZE=1027
250 2.1.0 <>... Sender ok
>>> RCPT To:<www-data@myserver>
>>> DATA
250 2.1.5 <www-data@myserver>... Recipient ok
354 Enter mail, end with "." on a line by itself
>>> .
050 <www-data@myserver>... Connecting to local...
050 <www-data@myserver>... Sent
250 2.0.0 t8IGojKw022539 Message accepted for delivery
www-data@myserver... Sent (t8IGojKw022539 Message accepted for delivery)
Closing connection to [127.0.0.1]
>>> QUIT
221 2.0.0 myserver. closing connection

Messages are delivered when I specify a real sender address:

echo "hello" | sendmail -vf "sender@realdomain.com" "xxx@gmail.com"

But why messages were delivered when it couldn't resolve it's own name, and not now?

Leonardo
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  • Post the configuration (in particular the output of sendmail -d0.1 </dev/null) with /etc/hosts reverted to the previous contents. Remote mail servers will rightly reject anything from the unqualified name of myserver.; this must be qualified to myserver.example.com or such. – thrig Sep 18 '15 at 17:20
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    Don't send to port 25 from a broken mail server. Read https://support.google.com/a/answer/176600?hl=en and send using authentication, which ensures Gmail knows who you are regardless of the configuration of your server. I could tell you how to do that with exim4 but I have forgotten everything I once knew about sendmail configuration, sorry. Note that if you are only sending to gmail addresses you don't even need to authenticate for the aspmx.l.google.com delivery host. – Chris Davies Sep 18 '15 at 17:23

1 Answers1

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Ok. I hate when it happens. I just found the solution after posting it. @thrig is right. It must be a fully qualified name. I've changed my "hosts" file to:

127.0.0.1 localhost localhost.local
127.0.0.1 myserver myserver.local

Now it works fine. Thank you all.

Leonardo
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  • Thank you for letting us know. Please accept your own answer - this stops StackExchange from bringing your post back to the front of the list every few weeks – Chris Davies Sep 18 '15 at 22:37
  • If my domain name is “inspvirtual.mx”, could you explain me what do I need to write? I don’t quite get it, and also, do I need to restart anything? – Aarón Gutiérrez May 26 '19 at 16:41