I thought this could be useful for other Namecheap customers.
'Namecheap’s Open-Xchange servers use only
'secure' connnections (STARTTLS, SSL/TLS). Supposing
domain.com is the domain you have purchased, you’ll have to configure Thunderbird using these settings:
; Username : your email address (@domain.com) ; Password : password you have set in the Namecheap configuration menu ; Incoming/outgoing servers : oxmail.registrar-servers.com ; Incoming server type : IMAP or POP3 ; Outgoing server (SMTP) : 465 port for SSL, 25 or 26 for TLS ; Incoming server (IMAP) : 993 port for SSL, 143 for TLS ; Incoming server (POP3) : 995 port for SSL 110 for TLS
That should do the work. I use POP3 with SSL/TLS (Port: 995). Be sure you use
'Normal password' as
authentication method. Voila !