Public Folder Replication and Message Size Limits
2011-01-29 Initial Post
Windows Server 2003 SP2
Exchange Server 2003 SP2
I was working on an issue where a PF wasn't replicating all of its content to another replica (there were only 2 replicas, each in a different routing group). There weren't any size limits on the folders or the PF stores on either server. I read a few PF replication troubleshooting articles and didn't really come up with a solution from reading then, although I did learn a lot about the PF replication process.
To make a long story short, the issue wasn't an issue. The items/posts that weren't replicating all had attachments over 20 MB in size. This MSExchange.org article states that "public folder replication uses this Virtual Server" in reference to the message size limits set on the SMTP virtual server. So it turns out that the 20,048 KB (20 MB) limit on the SMTP virtual serves of our bridgehead servers is what limited the PF from replicating the larger items. That same size limit is also set on the routing group connectors, SMTP connectors, and in global settings (I might have missed some others, but suffice to say, this org does not want to transfer messages that are over 20,048 KB).
I stumbled upon the answer when I took a good look at the folder replicas and found a discrepancy of 12 items between them (SiteA: 43 items, SiteB: 31 items). This matched up with the fact that there were 12 items over 20 MB. See images below.
It looks like in Exchange 5.5, those types of message size limits didn't affect PF replication. Per this MS KB, "Public folder replication messages are system messages, and are not subject to size restrictions by the message transfer agent, or by restrictions specified on a particular connector (such as the X.400 Connector)."
Message size limit on SMTP virtual server.
The 12 posts that didn't replicate were all larger than the size limit of 20 MB.
