address is specific to a box. For example, a public address redirects to a server inside. If the IMAP virtual server and the OWA virtual directories are on the same box then you would use the same address.
If you have a cert for OWA, you can use that cert for IMAP. Export it and import it to IMAP. But, if you do this the domain name for IMAP and OWA must match and IMAP and OWA must run on the same box.
The ssl port for IMAP is 993