http://www.spamhaus.org/query/ip/77.234.44.146 AUP#Out-1220.
Received the above message when trying to send an email. Can receive emails.
Alle antwurden (2)
Need help sending emails
If you tried to send email and got an error back from the server spam filter which told you to check your IP address then it means the smtp server filter is using spamhaus and it is blocking you.
You need to use the spamhaus link and follow advise on how to get your IP or email address off their database. That IP address is listed in the CSS Blocklist. It is believed that IP address has been sending out spam in bulk. So click on the link to get information. https://check.spamhaus.org/listed/?searchterm=77.234.44.146
This issue is not a problem with Thunderbird. You have to get it sorted before the server will allow you to send.