How to clear the IMAP settings in cache?

Hello together,
I have a (little) problem with IMAP-connecting. Everything worked yesterday, today there is no connection to IMAP-Folders. I asked the provider. He told me to clear the Settings-Cache and setup the connecting new, because he changed something on the server.

My question is: how can I can clear the IMAP settings in cache?

Понимаю - форум мёртв =(

Perhaps you can try deleting the Imap account and add it back to em CLient

It does not work.
I tried this first of all.