This is the standard setup with Microsoft Exchange Server.
MetaDefender Email Gateway Security can only be installed on Hub or Edge role Exchange Servers (2013 or 2016).
Exchange Server message expiration timeout
The MessageExpirationTimeout parameter of Microsoft Exchange Server specifies the maximum time that a particular message can remain in a queue.
If a message remains in the queue for longer than the MessageExpirationTimeout period of time, the message is returned to the sender as a permanent failure.
As a consequence this parameter is likely to affect the delivery of emails released or forwarded from Quarantine (see 4.3 Quarantine ) or emails retried from Audit > Email History (see 4.4 Email history ).
The default value of MessageExpirationTimeout is 2 days. It means that if an email spends more than 2 days in Quarantine or in Audit > Email History then releasing or forwarding and retrying (accordingly) after 2 days will fail.
MessageExpirationTimeout can be extended to the maximum of 90 days.
If MessageExpirationTimeout is set to a very low value (the lowest accepted value is 5 seconds) then it can even affect the delivery of emails going through the normal workflow (not quarantined, not failing).
Reference and further reading
Microsoft Exchange Server 2013: https://technet.microsoft.com/en-us/library/bb124238(v=exchg.150).aspx
Microsoft Exchange Server 2016: https://technet.microsoft.com/en-us/library/bb124238(v=exchg.160).aspx
How To Verify
To verify that the Exchange Transport Agent has been installed successfully, open the Exchange Management Shell and type 'Get-TransportAgent' [ENTER]
Ensure that MetaDefender Email Security Smtp Agent and MetaDefender Email Security Routing Agent are listed and their Enabled statuses are True.
Identity Enabled Priority
-------- ------- --------
Transport Rule Agent True 1
DLP Policy Agent True 2
Malware Agent False 3
Text Messaging Routing Agent True 4
Text Messaging Delivery Agent True 5
System Probe Drop Smtp Agent True 6
System Probe Drop Routing Agent True 7
Metadefender Email Security Smtp Agent True 8
Metadefender Email Security Routing Agent True 9