EX16-MB-000450 - The Exchange Outbound Connection Limit per Domain Count must be controlled.


Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous outbound connections from a domain as a delivery tuning mechanism. If the limit is too low, connections may be dropped. If the limit is too high, some domains may use a disproportionate resource share, denying access to other domains. Appropriate tuning reduces risk of data delay or loss.

By default, a limit of 20 simultaneous outbound connections from a domain should be sufficient. The value may be adjusted if justified by local site conditions.


Update the EDSP to specify the 'MaxPerDomainOutboundConnection' value or verify that this information is documented by the organization.

Open the Exchange Management Shell and enter the following command:

Set-TransportService -Identity <'IdentityName'> -MaxPerDomainOutboundConnections 20

Note: The <IdentityName> value must be in single quotes.


Enter the value as identified by the EDSP that has obtained a signoff with risk acceptance.

See Also


Item Details


References: 800-53|SC-5(2), CAT|III, CCI|CCI-001095, Rule-ID|SV-228389r879651_rule, STIG-ID|EX16-MB-000450, STIG-Legacy|SV-95403, STIG-Legacy|V-80693, Vuln-ID|V-228389

Plugin: Windows

Control ID: 50ea3c3408572eb2ec25e85c80bd45aa8238aa032d9a75d9f18da27f1d7988a7