I used up all possible combinations of hostname but I always either get a certificate error or just IMAP connection broken.
Certificate failure for imap.froiden.com: Server name does not match certificate: /O=imap.mailhostbox.com/OU=Go to https://www.thawte.com/repository/index.html/OU=Thawte SSL123 certificate/OU=Domain Validated/CN=imap.mailhostbox.com
Hostname which I used is '{imap.froiden.com}INBOX'. ANy suggestion to solve this error?
The certificate is plain invalid. You should either connect to imap.mailboxhost.com:993/imap/ssl or contact the administrator of the mail server and ask for a valid certificate.
Note that while you can use the connection string imap.froiden.com:993/imap/ssl/novalidate-cert to skip certificate validation, you should not do so as that flag will allow any Man In The Middle attacker to read and write your email.