I am having an issue where I cannot reclassify several junk email messages in MailGate to Junk.  When I select "Re-classify as Junk" a popup window appears and says “Message(s) cannot be submitted to Axway for reclassification.”

“Message(s) cannot be submitted to Axway for reclassification.” message is displayed when the message size exceeds the maximum spam size that MG addresses.

In order to increase the maximum message size which MG scans for spam, please navigate to:
MG Admin UI > Mail Policies > Anti-spam > Settings
Message Size Threshold
Scan Inbound Mail up to (KB):

The default value is 200kb.
Note that increasing this causes MG to scan bigger messages and as such presents a performance penalty.

You may set this to 500kb as this is the maximum message size for which our Message Protection Lab creates anti-spam filter definitions. Please proceed with the increase only if your appliance does not have performance-related issues.