SDB:E-Mails to T-Online Addresses are Not Delivered

Version: 6.3

Symptom

You have defined sendmail as SMTP server in your configuration. Your provider is T-Online and you want to send messages to t-online.de addresses. However, these messages are not accepted by the T-Online mail server and you receive instead an error message similar to this:

<xy@t-online.de>... Deferred: Connection refused by
 mailin03.sul.t-online.de.
Message could not be delivered for 5 days
Message will be deleted from queue

Cause

mailin03.sul.t-online.de is one of the MX used for the delivery of messages from outside the T-Online network to T-Online customers. These computers are blocked by a firewall on the T-Online network.

Solution

Configure sendmail in such a way that messages to t-online.de addresses are sent through a mail relay accessible within the T-Online network.

First, register on the homepage of the provider for smtprelay.t-online.de under http://www.t-online.de/service/inhalte/kemsviea.htm .

Now you can configure the file /etc/mail/mailertable to have messages to T-Online addresses sent via this relay. As for the rest of messages, sendmail will continue to send them directly.

For this purpose, insert the following entry in the file /etc/mail/mailertable:

t-online.de            smtp:smtprelay.t-online.de

In order to validate the changes, enter the following command as administrator root:

SuSEconfig
rcsendmail restart

If you observe that e-mails to other domains cannot be delivered either, then you can send all e-mails via the smtprelay. In this case, do not proceed as described above but edit the following variable in the file /etc/rc.config.d/sendmail.rc.config instead:

SENDMAIL_SMARTHOST="smtprelay.t-online.de"

Finally, execute SuSEconfig and rcsendmail restart once again.

Please note that this solution approach exceeds the scope of our free installation support.

From SuSE Linux Version 8.0 on, the variable SENDMAIL_SMARTHOST can be found in the file /etc/sysconfig/sendmail.

<keyword>sendmail,mail,t-online,smtprelay,relay,mailertable</keyword>