[Evolution] Inacceptable TLS certificate

[jan public famvlug nl]

Hello,

I use IMAP with 'STARTTLS after connecting' for fetching email in Evolution.
After a while, my email provider changed the certificate. This certificate
did not correspond to my domain, so I got a warning and a question whether
I would like to accept this certificate.
Initially, I did not accept it because I wanted to investigate the
certificate first. This resulted (obviously) in the fact that I could not
get my email any more due to an 'inacceptable TLS certificate'.

My question is now:
How can I now I trust the certificate accept the certificate, so that I
can retrieve my mail again.

Best regards,
Jan.