Exchange Transport Dumpster Test

The transport dumpster is a feature of the Hub Transport server role that submits recently delivered mail after an unscheduled outage. The transport dumpster should always be turned on when using CCR or local continuous replication (LCR). The transport dumpster is enabled organization wide by setting the amount of storage available per storage group and setting the time to retain mail in the transport dumpster. If either of these settings are violated in real-time, then the transport dumpster starts deleting mails.

Using this test, you can closely monitor the transport dumpster and the mails within, determine how often the Exchange server experienced outages, and also figure out whether any critical mails were lost during downtime.

Target of the test : A server configured with the Hub Transport role

Agent deploying the test : An internal agent

Outputs of the test : One set of results for the Hub Transport server being monitored.

Configurable parameters for the test
Parameters Description

Test Period

How often should the test be executed.


Indicates the IP address of the Hub Transport server.


The port number of the Hub Transport server. By default, this is 691.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Overall size of the Dumpster

Indicates the total size of the mail items(in bytes) that are currently in the transport dumpster on this server.


A low value is typically desired for this measure. A very high value or a value that increases consistently could reveal a prolonged outage. If the value exceeds or is dangerously close to the value of the MaxDumpsterSizePerStorageGroup parameter, it could mean that mails will soon be deleted from the dumpster.

Dumpster inserts rate

Indicates the rate at which mails were inserted in the dumpster.



Number of current items

Indicates the total number of mail items that are currently available in the transport dumpster on this server.


A low value is typically desired for this measure. A very high value or a value that increases consistently could reveal a prolonged outage.

Dumpster deletions rate

Indicates the rate at which items were deleted from the dumpster.


A high rate of deletion is typically indicative of the frequent violation of the MaxDumpsterSizePerStorageGroup and/or the MaxDumpsterTime setting. These parameters have been discussed below:

  • MaxDumpsterSizePerStorageGroup: This parameter specifies the maximum size of the transport dumpster queue for each storage group. It is recommended that you set this to a size that is 1.5 times the size of the maximum message that can be sent in the organization. If the organization has no size limits, we recommend you configure the MaxDumpsterSizePerStorageGroup parameter to a size that is 1.5 times the size of the average message size sent in the organization. For example, if the maximum size for messages is 10 megabytes (MB), you should configure the MaxDumpsterSizePerStorageGroup parameter with a value of 15 MB.
  • MaxDumpsterTime: This parameter specifies how long an e-mail message should remain in the transport dumpster queue, to a value of 07.00:00:00, which is 7 days. This amount of time is sufficient to allow for an extended outage to occur without loss of e-mail.

When using the transport dumpster feature, additional disk space is needed on the Hub Transport server to host the transport dumpster queues. The amount of storage space required is approximately equal to the value of MaxDumpsterSizePerStorageGroup multiplied by the number of storage groups.

If you do not configure the transport dumpster, the default values are used. The default value for the MaxDumpsterSizePerStorageGroup parameter is 18 MB and the default value for the MaxDumpsterTime parameter is 7 days. If either the size limit or time limit is reached, messages are removed from the transport dumpster queue by order of first in, first out.