Problem: Suddenly stop sending

What I already did: he is in online mode
and have reinstalled over it. With my other clients? everything unchanged
Windows 10 1903 with 64 BIT with built-in Defender

What I want to send is moved to the Outbox and is marked with a red one - stays there. Until recently, it was still. Question, what else can it be?

I think I could solve it:
I deleted my account in the settings and after entering my email address and the email password, it was automatically restored

Unfortunately, now is my formatting (columns and width) is back to default