Exchange Server - troubleshooting general delays?

Lately we have seen many reports from users that their email is delayed.

What they are describing in most cases we have determined to be one of the following symptoms:

1)Mail that external users send our users took 10+ minutes to show up. This happens with some and not others, and it is not domain specific but seems more time-of-day specific.

2)Mail that they send will go to Outbox, but not Sent, and will not send unless they open the item in Outbox and resend it.

3) If they are using Outlook(all are in online mode), they also sometimes have issues clicking on a folder within Outlook (e.g. opening "Inbox" or a custom "HR Emails" folder). This sometimes gives them a "The Outlook window could not be opened... The information store could not be opened." message.

All of these issues resolve themselves almost immediately; sometimes going to the Outbox and resending the email right when you notice it didn't send will solve it. You can also simply dismiss the "information store could not be opened" and try immediately to get into that same folder. Sometimes, you need to wait a few seconds and keep dismissing the same message, but you will be able to get in.

It sort of looks like the server is busy when these 'requests' are coming in.

This has started happening more and more frequently over the last month.

A little about our environment:

-Migrated from Exchange 2007 to 2013 about 12-18 months ago. This was done from old hardware to new hardware, on a fresh Server 2012 install.

-Between the Exchange upgrade and today, we created a second virtual domain controller to set up a second AD forest. This uses a resource forest configuration to 'share' the one Exchange server with our original forest.

-Each forest has a database file that the mailbox users in that forest will be stored: the original database had grown to 300GB from around 230GB since the migration. The second database file (.edb) is 40GB.

What I need answered:

Are any of these possible factors in what appears to be a slow degradation of our email system quality?
With the message about the information store, it sounds like it is having trouble reading from this edb file?

We only have a few users on the second domain so it is not definitive, but I cannot remember a time they complained of the same delays as a user on the second edb file. Could our database file possibly degrade over time?

Is there anything we can do to maintain this quality? This same file has been around for years, and is probably very fragmented if nothing else. Is this okay to assume as a factor in our issues?

Any help in where to start troubleshooting nondescript issues would be much appreciated!

Thanks in advance,
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Kash2nd Line EngineerCommented:
not an easy thing to troubleshoot.

To rule out possibility of DB, you could create a new blank database and migrated couple of users to that newly created DB and then test send and receive.

Also has there been any recent changes in your ISP or DNS, I would also run tests on the domain. Are you using any smart host to send out / receive in or sending direct.

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BMFCAuthor Commented:
This was a difficult question to answer, and I appreciate how useful the direction you gave was. We have not resolved the issue but it has not progressed either. We may re open this item when there is more time.
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