Thunderbird Autoconfig Thunderbird can auto-detect IMAP/SMTP/POP3 settings by looking at the domain's "autoconfig" DNS record. CNAME record A typical CNAME record looks like this: Name: autoconfig TTL: 3600 RR Type: CNAME Target: host.name.com BIND example: Domain: autoconfigTTL: 14440Record Type: CNAMERecord: host.name.com. Please make sure to add CNAME record in your domain's DNS zone to have the autoconfig feature in Thunderbird working. CrossBox Standalone version exposes the autoconfig for Thunderbird clients at: https://host.name.com/mail/config-v1.1.xml host.name.com is the hostname of the server where CrossBox is running. Manual Configuration If you don't want to use the autoconfig feature, you can still configure IMAP/SMTP/POP3 settings in Thunderbird manually. Server Information Incoming Mail Server: host.name.comOutgoing Mail Server (SMTP): host.name.com Logon Information Username: email@example.com Advanced Settings Incoming IMAP Recommended Port: 993SSL: SSL/TLSAuthentication: Normal password Optional Port: 143SSL: STARTTLS or NONEAuthentication: Normal password POP3 Recommended Port: 995SSL: SSL/TLSAuthentication: Normal password Optional Port: 110SSL: STARTTLS or NONEAuthentication: Normal password Outgoing SMTP Recommended Port: 465SSL: SSL/TLSAuthentication: Normal password Optional Port: 587SSL: STARTTLS or NONEĀ (STARTTLS for standalone and None for Cluster)Authentication: Normal password