Hello
A few Tips about Groupware/Webgroupware products on SME6/7:
As long as the Groupware uses an existing Mailer and doesn't bring it's own, you're fine. Most Groupware uses the existing mailer like Postfix, Sendmail, Qmail or Exim. I'm referring to "mailer" as the combination of programs that provide you with IMAP and SMTP Services. I NEVER use POP3, that's for lusers.
The Web-Frontend of SME 6/7 is based on Horde, another Web-Groupware. Web-Groupware runs on a Webserver and doesn't usually provide out-of-the box stuff like Mapi, a GUI Client (eg.: Notes, Groupwise, Outlook) which provide Client GUI based Address-Books, Calendars, etc.
Other Web-Frontends include Open-Xchange, eGroupware, MoreGroupware, PHPGroupware, all of which can run at the same time on a SME 7 Server.
I'm personally using MoreGroupware for those who need Groupware, the others use the built-in Horde Groupware.
I can access my Mail using Horde (Webmail) or MoreGroupware, both display the same status (read mail, etc.).
Disadvantages:
Horde on SME uses the built-in SSO (Single-Sign On). if you change your SME Password, Horde is informed and uses the newer Password.
You'll have to manually adapt any Web-Groupware to lock into the SME Password mechanisms, or revert to changing your Passwords in several places.
As an old Novell hand still running servers 3.12, 3.2, 4.11, 5.0, 5.1 and 6.0 I've had a look at the Hula Project. It used to be Novells quite powerful Mail-solution... It doesn't quite fit in with my requirements, so I didn't further it.