Can´t receive E-Mails since yesterday

I can´t receive E-Mails from different accounts. Some work, but three won´t. I did not change any settings.

The message: [IMAP] MailClient.Accounts.ConnectionException: Der Server unterstützt keine sichere Verbindung, dadurch kann keine sichere Verbindung hergestellt werden.

Many thanks in advance for your efforts.

The fact that you “did not change any settings” begs the question as to whether you have contacted/visited the email hosts to make sure they have not changed anything with connection settings, etc. It is not unheard of for email hosts to not notify you of changes.

Posting account settings of those that are problematic, along with the host names of those email hosts will give us some information to start from.

Thanks for your quick response!

IMAP Host:
IMAP Server Port: 143
SMTP: Port: 587

I tried to make a diagnosis. SMTP is OK, IMAP is the problem. I tried
to “repair” which doesn´t work. “access data has been delined.”

What version of eMC are you running?

Have you contacted/visited your mail host (the ones that are problematic)?

Have you tried to REMOVE and RE-ADD the problematic accounts?

Please go to Menu > Accounts and click on the IMAP tab for the account.
For port 143, set the security policy to Use SSL/TLS if available

Next go to the SMTP tab.
For port 587, set the security policy to Force usage of SSL/TLS