I have an ISP smtp server that I'm happy to use and is super fast of course.
I have a separate account who's MX records are gmail, so while it looks like I have email@example.com, I just go to gmail to use the account.
If I add firstname.lastname@example.org as a gmail account, I get all the features of Zimbra's syncing like contacts and calendar which are important - but I'd like to modify the "send mail as" settings, and I figured the only way to do that would be to add Gmail as an IMAP account. But, when I do that, I don't get all the calendar and contact synching.
I think ideally, I would add the email@example.com account, then add a separate SMTP account for sending that is my ISP and sends mail from that firstname.lastname@example.org
Furthermore, when adding gmail as an IMAP service, all my little folders show up under a [Gmail] folder, with sub-dirs of Drafts, Sent Mail, etc. I wish that mail would show up in the default folders.