Calendar invites sent to deleted items

[Simon Smith]

Hi,

I've got an issue with my domain. Whenever a user creates a calendar appointment request the email notification automatically gets sent to the deleted items box.

I've done a message trace and I can see

The message was delivered to the Deleted Items folder.

There's no rules set for the users, and I can't see any settings in the Exchange Admin console that would affect this. 

Any suggestions?

[#2]

Automatic processing might trigger this, check the options under Calendar > Automatic accept or decline > Auto accept/decline. Another possibility is a hidden rule, check via MFCMAPI or similar low level tools.