Inspect the certificate - see attached screenshot for instructions.

Please post a screenshot of the Certificate Viewer window with the 'Issued To' information visible.

Here are the certificate screenshots - and thanks for a prompt reply!

As per your screenshot, Thunderbird is trying to access the server mail.lifestylediet.space. However, the cert has been issued for *.web-hosting.com. There's a mismatch, and this is what Thunderbird is complaining about. You should talk to your email provider.

Thank you christ1 ! I will

lifestyledietspace said

Thank you christ1 ! I will

Or accept that the certificate is valid and create an exception. This is one of those occasions where you get to use your brain. If you host your server with web-hosting, then having their certificate is not going to be an issue as you sort of expect it. You have not paid for your own certificate after all and you have chosen to use encrypted communications STARTTLS which requires a certificate.

This is where the human has to make a discussion, is it ok or not. You can ask here, you can ask at your provider. But in the end you have to make a decision.

Are you sure the server settings are correct? I believe namecheap.com is your host, and according to their instructions, the security on IMAP port 143 and smtp port 587 is None. For SSL/TLS security, the IMAP port is 993 and the smtp port is 465.

thank you all for your help with this one and it was solved with the help of namecheap hosting.