When an inbound email contains more than 20 attachments, only the first 20 files are attached to the new note that the Mail API generates.
What’s new is that in such cases the following message gets added at the bottom of the note: “Not all attachments from the email were added to this note (maximum allowed is 20)”.

When administrators or auditors review the email that was sent to the Mail API in the Inbound Email section of the Settings console, they will see the same message whenever an email contained more than 20 attachments. Note that the inline images included in the inbound email also count as attachments.

A Letter From Our CEO: What I've Learned, What I Believe, and Where We're Headed Together
When I joined Xurrent as CEO in February, I made a commitment to myself before I made any commitments publicly: I would listen before I led. I would get in front of customers, sit down with our partners, and spend real time with the incredible team that built this platform — before I said a word about where I thought we were going.

Xurrent named a Market Leader in Research In Action’s Vendor Selection Matrix™ for IT & Enterprise Service Management Solutions
Xurrent earns #1 rankings in customer satisfaction, price vs value, and recommendation index in Research In Action's global ITSM/ESM Vendor Selection Matrix report.

