I have 2 VS in LTM with same IP Address but with different ports-HTTPS and SMTP. In the BIG-IP DNS, I created 1 wide-ip but used only HTTPS VS. I created a CName for the wide-ip. All of the services will use the same FQDN. Do I need to create wide-ip for SMTP and CName for that as well?
WideIPs respond to a name query with an IP address. The specific port has no role in name resolution.
The specified port may be used for configuring monitoring, but that is it.
However, you may want to have a different name (possibly a CNAME) for the SMTP service (mail.domain.com) - that's a different choice.