The following TCP ports need to be open in order for Zimbra to work properly:
- POP3 - port 110
- IMAP - port 143
- SMTP - port 25
- HTTP - port 80
- HTTPS - port 443
- Secure SMTP (SSMTP) - port 465
- Secure IMAP (IMAP4-SSL) - port 585
- IMAP4 over SSL (IMAPS) - port 993 - NECESSARY FOR iPHONE CONNECTIVITY
- Secure POP3 (SSL-POP) - port 995
