OAB messages and message size restrictions

I had a chance to work a pretty interesting OAB issue with a co-worker the other day. We had a situation where Outlook clients from Site B were downloading their OAB just fine before midnight, and as soon as 7 am rolled around everything for the users in Site B came to a screeching halt. One thing that we did know was that this OAB was a replica from Site A.

Now this is common for large organizations to generate an Offline Address Lists, and then replicate them to other Exchange sites. But if things are not configured properly this can lead to problems.

Being that this was a replica, that kind of pointed us in the direction that we needed to go in to solve this issue.

Throughout the troubleshooting process we ran various tests and checked everything from the OAB folders; the posts in the store, etc and everything looked just fine. The OAB even generated fine in Site A.

So, we were able to fix this by doing the following:

1. Ran OABInteg /s:exchsrvname /t:oabfldcheck /v:2 /l against the public folder information store so we could get the OAB message and attachment sizes. Here is the summary at the end of the oabfldcheck test.

Scan Completed

+------------+

Message Class Normal found: 2

Message Class Differential found: 18

Message Class Unknown found: 0

Message Attachments found: 174

Messages found but unable to read the properties: 0

System folders found: 3

Highest sequence number found: 23

Lowest sequence number found: 15

Biggest attachment found: 6700 Bytes

Smallest attachment found: 106 Bytes

Biggest message found: 11358214 Bytes <--- This is what we want!!

Smallest message found: 305 Bytes

2. Looked for Biggest message size and we found this in the Scan Completed section of the test .(end of the test).

3. Searched up for 11358214 in the c:\OABInteg.log file. 11358214 is the Biggest Message size. Below is what we find.

Message Conversation Topic: \Global Address List - details_u.oab - 23

Message OAB Name: \Global Address List

Message OAB DN: /

OAB Normal Message class

Message Code Page: 0x4e4

Message Size: 11358214 Bytes

Message Local Id: 0x409

Message OAB Sequence: 23

OAB Container GUID: ef06e64f-8ced-490e-aad0-f8030fa109b4

4. Being that this was a routing issue the next thing we checked was the message size restrictions on the SMTP connectors, and we saw that they were set to restrict messages that were over 10 MB in size. So this message was not going to replicate once it hit 10 MB, and you can see that it is a little over 11 MB.

Note on Message Restrictions - The routing engine determines the message size, priority, and message type (that is, system or non-system message). The routing engine compares these properties with available connector restriction information. It then excludes those connectors that cannot transfer the message due to effective connector restrictions from the list of potential connectors.

5. The Fix was to reconfigure the message restriction size limits to restrict message of 15 MB or greater. Once this was done we forced replication and the messages were able to replicate from Site A to Site B. We had the Outlook clients log out and then back in to Outlook and they were again able to download their OAB.

With this being said, when your organization is growing make sure that you configure your message restriction sizes limits so that they do not block your OAB messages from replicating around.

Dave