Sometimes, where using Outlook to reply/forward messages the message is completely lost, not sent to the recipients and I can see this kind of error on postfix logs:

maillog:Nov 7 17:01:34 linux1 postfix/smtpd[22758]: F0050378610: reject: RCPT from smtp.mydomain.com[x.y.z.w]: 504 <'Alexandra '>: Recipient address rejected: need fully-qualified address; from=<my.name@mydomain.com> to=<'Alexandra '> proto=ESMTP helo=<zimbra.mydomain.com>

The account was exported to .psf and then imported using Zimbra Import tool.

The message being replied/forwarded doesn't stay on Drafts, Sent or any folder I could find, its totally gone (and this is tha worst part).

Checking the server policies, I don't have any of the checkboxes for "Protocol checks" or "DNS checks" (under Global Settings) active.

I have some reports from some users that if they remove all the recipients Outlook automatically fills in and then entering them all again by hand solves the problem, but I don't consider this a solution.

Whats wrong here? Outlook? the Connector?

Thanks for any help.