Roadrunner marks Thunderbird outgoing email as spam
When Roadrunner receives an email sent by me through Thunderbird it marks the email as spam. No other servers do this.
Alle antwurden (6)
Then you should complain to Roadrunner.
Tested by creating and sending directly on Roadrunner Webmail: no problem, so they say it's something in Thunderbird.
Using webmail and sending through a SMTP server are two different things. That result is meaningless. Too bad the RR people are not smart enough to know that. Do you use a signature? If so disable that and try again.
No signature is used. Today Roadrunner "support" guy told me to solve it by sending a message to all my Roadrunner contacts telling them to unblock my messages! Think about that for a minute... send a message to the contacts that Roadrunner won't allow to read my messages!
Most of those help desk people only know to pick up the phone when it makes a noise. Pretty sad.
Maybe you send your message in HTML? Try sending in plain text or in both HTML and plain text to see if that helps.
Check under Tools -> Options -> Composition -> General -> Send Options and/or Tools -> Account Settings -> Composition & Addressing -> Composition -> Compose message in HTML.