Event ID - 2166

Event Id2166
SourceMSExchangeMTA
DescriptionA call from %1 process %2 was completed, adding object %3 to queue %4. Queue %4 now contains %5 items. [%6 %7 %8 %9] (6)
Event InformationAccording to Microsoft:
The message transfer agent (MTA) may take a long time to start if there is a large number of DB*.DAT files in the MTADATA directory when the service is restarted. This is normal and expected behavior but is often misinterpreted as a problem. Administrators often mistakenly believe that the MTA is not responding and they complicate the issue by stopping the MTA service.
When the MTA starts, up it has to rebuild the queues in memory. If there are a lot of DAT files, this can take quite some time.One quick check you can perform is to set the MTAs logging on Field Engineering to Maximum and then monitor the 2166 and 2167 events for the number of objects in each of the queues. There is no hard and fast rule, but if you have 100,000 DAT files at startup, it is reasonable to expect the queues to grow to at least that total size before assuming the MTA is not responding.
Reference LinksXCON: MTA Taking a Long Time to Start

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