Exchange 2003 to 2007 Migration issues mail stops flowing.

We’re in the middle of migrating one of our clients from Exchange 2003 to Exchange 2007. As part of that we currently have both Exchange servers in the domain and therefore some users on one version and some of the other version. Today we got a call because the users on Exchange 2007 were not receiving any email. Those on Exchange 2003 were. All users could send mail without an issue. The client has onsite IT staff and last night they moved the majority of the users from Exchange 2003 over to Exchange 2007 via the move mailbox wizard. I connected in to the site and from SVR1 (Exchange 2003), I could see in the Queue viewer that there were about 180 email messages waiting to go to SVR5 (Exchange 2007). I did a telnet from SVR1 to SVR5 on port 25 to test connectivity. I got the response below.

Interesting I’ve not seen that before. I did the same on SVR5 itself to Localhost port 25 same result.

I checked the event logs and found the following message the application log on SVR5

Event Type: Warning

Event Source: MSExchangeTransport

Event Category: ResourceManager

Event ID: 15002

Date: 6/09/2007

Time: 1:19:01 PM

User: N/A

Computer: SERVERNAME

Description:

The resource pressure is constant at High. Statistics:

Queue database and disk space (“C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue\mail.que”) = 89% [High] [Normal=82% MediumHigh=84% High=86%]

Queue database logging disk space (“C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue\”) = 89% [Normal] [Normal=94% MediumHigh=96% High=98%]

Version buckets = 1 [Normal] [Normal=40 MediumHigh=60 High=100]

Private bytes = 6% [Normal] [Normal=71% MediumHigh=73% High=75%]

Physical memory load = 88% [limit is 94% to start dehydrating messages.]

Inbound mail submission from other Hub Transport servers, the Internet, the Pickup directory, the Replay directory, and the Mailbox server, if it is on a Hub Transport server, has stopped.

Loading of e-mail from the queuing database, if available, continues.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

Ok disk space is an issue. I checked and sure enough the C: drive had 3.2GB free space (our of 30GB). I investigated a bit further and found that there was 17GB of Exchange 2007 Log files (little 1MB files) in there. These had been generated by the system during the mailboxes being moved from SVR1 to SVR5. At this point we could have either moved the log files to another volume on SVR5 or turned on Circular logging. We needed the problem resolved fast and decided to turn on Circular logging. Once done we dismounted and remounted the Exchange database and we have our disk space back. We went back to SVR1 in the Queue viewer and forced connection of that Routing Group connector and within minutes, the 190 messages that were now there flowed through to SVR1.

Key takeaway Exchange 2007 handles resource monitoring very differently to Exchange 2003 make sure you keep an eye on disk space and don’t forget the basics when troubleshooting.