I can only assume we have a setting issue then. Given Microsoft clients go for the minimum security

I can only assume we have a setting issue then. Given Microsoft clients go for the minimum security and Thunderbird tends to go for the highest. it will probably be in the SSL/TLS or password transmission type.

Please add the Mail and News Accounts from troubleshooting information to your post To find the Troubleshooting information:

Open Help (or click on three-line-icon and select Help)

Choose Troubleshooting Information

Use the button Copy to clipboard to select all. Do not check box "Include account names"!

Paste this in your post.