You have configured Exclaimer Cloud - Signatures for Microsoft 365, and you notice that signatures are not applied to Out of Office emails or automatic replies.
When automatic replies are sent from Microsoft 365, the MAIL FROM: information on the envelope is intentionally left blank by Microsoft Exchange.
For Exclaimer Cloud to determine which user signature to apply, then deliver the email back to Microsoft 365, it is essential that the MAIL FROM: information is provided with the email. If automatic replies are sent to Exclaimer Cloud, they will fail, as it is not possible to determine the correct route back to Microsoft 365.
As automatic replies are sent without a MAIL FROM: address, a mail flow rule is created in Exchange Online - this ensures that these emails are not routed to Exclaimer Cloud, thus preventing the issues mentioned above.
The mail flow rule is called Prevent Out of Office messages being sent to Exclaimer Cloud and is automatically created when you connect Exclaimer Cloud to Microsoft 365.
If the Prevent Out of Office messages being sent to Exclaimer Cloud rule is missing, then you can re-run the connector setup wizard to recreate this.