Outlook Mail stuck? It may not be your profile.

During a recent Exchange 2010 training, our instructor went through a couple of things that could be causing mail to not leave an Outlook or OWA client during normal operations.  When I did a few searches on this topic, I was alarmed to see that many people suggest that the problem is the Outlook offline storage file or PST.  While that does sometimes cause these issues (especially if you’re on Exchange 2003 or earlier), there are a couple of quick checks you should make against the server first.

On Exchange 2007 and 2010, if mail is getting stuck in users’ Outboxes on various clients, check two things:

1 – Is there less than 4GB of disk space available on any volume on the servers that contains Exchange data and/or queues? If there is less than 4GB, Backpressure protocols kick in, and Transport Services won’t move mail anywhere, leaving new messages stuck in users’ Outboxes. This is fixed by freeing up drive space or moving the database and/or queues to another volume with more room.

2 – If the disk space is ok, check to see if the Transport Services (which vary depending on your Exchange version) are running.  Any service that isn’t started can cause mail routing to fail, and messages to stay on the client software.  Obviously, to fix this you either need to get the services up or bring another Hub/Transport system online to handle mail flow.

Additionally, if you are using Exchange 2010, mail may get stuck in the Drafts folder.  That is to say, it leaves the Outbox and immediately appears in the Drafts folder in Outlook.  If you see this behavior, check to ensure that the Mail Submission service is running on your CAS server.  If it isn’t, mail can’t be properly picked up from the Outlook client, and the resulting error shoves the email into the Drafts folder.

Granted, if these issues are not the cause of your issue, or if it only seems to be happening to one user, then rebuilding the OST or PST might be in order.  However before you disrupt clients day-to-day activities, a quick check of the server might uncover a correctable error that can be quickly contained.  In the case of lack of disk space, it can even expose a growing problem that must be dealt with in the near future to avoid much more wide-spread downtime.