I run into the same problems with notifications via SMTP server "posteo.de", port 587 and SSL/TL until I entered "mail.posteo.de" as SMTP server instead of just "posteo.de". It works now as desired.
I run into the same problems with notifications via SMTP server "posteo.de", port 587 and SSL/TL until I entered "mail.posteo.de" as SMTP server instead of just "posteo.de". It works now as desired.