Users unable to accept shared calendar invitation from external users (stlfasteners.com). : Mismo Systems

Troubleshooting:

Users of ‘sterlinggtake.com’ were unable to accept the shared calendar invitation from external users (stlfasteners.com).
However, ‘stlfasteners.com’ users were able to accept the similar invites sent by 'sterlinggtake.com' users.
The calendar sharing email invite is attached to another email when received by the end recipient.
The mail attachment has ‘Accept’ button but it fails with error ' The operation failed'.
Checking an affected email, found ‘Disclaimer’ text added to it (from sender side) and the calendar sharing invite is added as an attachment which is an unexpected behaviour.
Checked the respective 'Disclaimer' rule and added 'sudhir.yadav@sterlinggtake.com' as an exception.
Tried to send a new calendaring sharing invite from Vinay (stlfasteners.com) and confirmed it started working as expected.
As suspected earlier, disclaimer rule was causing the issue. An exception was added to the disclaimer rule for all emails send to 'sterlinggtake.com’ domain as per the requirement.
Confirmed its working as expected and able to accept the external calendar sharing invite.

Users unable to accept shared calendar invitation from external users (stlfasteners.com). Print