OK, this may have been discussed elsewhere, but I having a hard time searching due to the very common search terms. Since upgrading to 5.0.10 we have been noticing messages showing up with an "On Behalf Of" line in the web client for messages sent from other Zimbra users. The thing is I can't seem to figure out any rhyme or reason to it. For example, a user sent me a message at 12:15 PM today and it did not include the line. She sent me another message at 2:37 PM and it had the "On Behalf Of" line. Both messages were sent to me only, and they were not forwards or responses.
Personally, it doesn't bother me at all, but I'm starting to get questions about why this is happening, and I don't know what to tell the users.