I use a T-Online/Speedport router and have email sending issues.
For Telekom customers, there may be email sending issues due to restrictions in the automatic router configuration. This mainly concerns customers with certain Speedport router models. Often, the server we use mail.routing.net is not automatically included in the “secure mail server list” in the router settings, resulting in its blocking as a potential spam sender. Please therefore add the entry mail.routing.net to the “secure mail server list” to ensure the sending of your emails.
If this exception rule does not resolve the issue, it is also possible to disable filtering by the “secure mail server list”, thus allowing emails to be sent from servers unknown to Telekom.
Another possible cause of email sending errors could be a general blocking of the standard SMTP port 25 by Telekom. We recommend using port 587 instead.
If you are not sure whether your email sending is actually blocked due to a Telekom setting, you can check it by sending a test email via Webmailer. No specific port configuration is then required, so if sending succeeds, the sending issue is probably due to local settings. You can access the Webmailer at https://webmail.routing.net.