Hello everyone, before thanks Zimbra to exists !!
For johjoh2k "the email certification" in Italy is very complex, is not a simple signature or discalimer.
Here you can find the official documents: http://www.cnipa.gov.it/site/it-it/A...ficata__(PEC)/
I think is not possible to integrate with Zimbra, but you need to create a specific mail server with a modified postfix or other MTA.
Intel Xeon Quad 4x 2.83+ GHz 12 MB L2 - FSB 1333 3Ware RAID1 2x750 GB SATA2 8 GB DDR2
Minimal Centos 5.3 64 bit - About 1000 users