Delayed emails in Exchange

This just started happening yesterday on our Exchange server (version 2010). I noticed some emails stuck in the queue with an error message 400 4.4.7 message delayed. To an external user I can possibly understand why but these are internal emails within the company from one user to another user.

For example, this is just an alert that comes from Ping Plotter.

Identity: CTEXCH01\99073\13693744
Subject: PingPlotter Auto-Alert! Latency Over 400ms Detected!
Internet Message ID: <c642cbe3-fdcc-409b-9055-96e6b25b0c2e@CTEXCH01.ctitle.local>
From Address:
Status: Ready
Size (KB): 2
Message Source Name: SMTP:AllowedtoRelay
Source IP:
SCL: 0
Date Received: 7/17/2015 5:21:17 AM
Expiration Time: 7/19/2015 5:21:17 AM
Last Error: 400 4.4.7 Message delayed
Queue ID: CTEXCH01\99073

Another example
Identity: CTEXCH01\99073\13693964
Subject: xxxxxxx
Internet Message ID: <99EF42C991E1294F9257BAD247946C1AC8209B@CTEXCH02.ctitle.local>
From Address:
Status: Ready
Size (KB): 2458
Message Source Name: FromLocal
Source IP:
SCL: -1
Date Received: 7/17/2015 9:27:16 AM
Expiration Time: 7/19/2015 9:27:16 AM
Last Error:
Queue ID: CTEXCH01\99073

Other emails I am seeing in there from 3 hours ago yet there is no last error on them. Our exchange is a few years behind on updates but we are forbidden to upgrade it at the moment via management. Otherwise I'm not sure what is causing this.
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stlhostAuthor Commented:
Thanks, but it didn't offer me any clues to what could be wrong. Actually didnt show any issues
stlhostAuthor Commented:
Turned out to be a bad DNS entry

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stlhostAuthor Commented:
bad dns entry
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