In SOGo config file, you can find several debug options, like below:
// Enable verbose logging. Reference:
// http://www.sogo.nu/nc/support/faq/article/how-to-enable-more-verbose-logging-in-sogo.html
//SOGoDebugRequests = YES;
//SOGoEASDebugEnabled = YES;
//ImapDebugEnabled = YES;
//LDAPDebugEnabled = YES;
//MySQL4DebugEnabled = YES;
//PGDebugEnabled = YES;
Please uncomment the one you need, then restart SOGo service. You can find
debug log in its log file /var/log/sogo/sogo.log
.