Issue
Cannot verify that Mail SNI (Domain SNI) SSL/TLS for IMAP/POP3/SMTP works in cPanel and a proper certificate is installed.
Resolution
To verify SSL please use the following commands:
1 – IMAP via SSL uses 993 port by default:
a. Connect to mail server using openssl:
openssl s_client -servername maildomain.com -connect maildomain.com:993
b. Check output and make sure that valid certificate is shown:
Server certificate
subject=/OU=Domain Control Validated/OU=EssentialSSL Wildcard/CN=mail.example.com
issuer=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA
c. Make sure that you received IMAP server response:
* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA AUTH=CRAM-MD5 AUTH=PLAIN IDLE ACL ACL2=UNION] Courier-IMAP ready. Copyright 1998-2004 Double Precision, Inc. See COPYING for distribution information.
2 – POP3 via SSL uses 995 port by default:
a. connect to mail server using openssl:
openssl s_client -servername maildomain.com -connect maildomain.com:995
b. Check output and make sure that valid certificate is shown:
Server certificate
subject=/OU=Domain Control Validated/OU=EssentialSSL Wildcard/CN=mail.example.com
issuer=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA
c. Make sure that you received POP3 server response:
+OK Hello there. <1793.1385684315@localhost.localdomain>
3 – SMTP via SSL uses 465 port by default:
a. connect to mail server using openssl:
openssl s_client -servername maildomain.com -connect maildomain.com:465
b. Check output and make sure that valid certificate is shown:
Server certificate
subject=/OU=Domain Control Validated/OU=EssentialSSL Wildcard/CN=mail.example.com
issuer=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA
c. Make sure that you received SMTP server response:
220 mail.example.com ESMTP Postfix