The altermime disclaimer method (Adding a disclaimer (altermime) or footer - Zimbra :: Wiki) had been working for us. Recently (after upgrading 5.0.9 -> 5.0.15), messages with a period at character 77 started showing only the characters prior to the period.
Forum thread http://www.zimbra.com/forums/adminis...-messages.html, discusses a similar problem. The altermime disclaimer method was implicated as the culprit. To test this in my environment, I commented the lines added to postfix master.cf.in out, and restarted postfix. The "period behavior" was gone. Uncommenting the postfix config filter lines, the behavior came back.
Any ideas would be welcome.