We have an OSTicket system that's been used for several years. It's currently at 1.15.6.
The default email to which clients can send a support request receives and processes attachments as intended. We added another email to capture a different group of support requests, but that email cannot pull ZIP attachments into the ticket. I can add attachments to those tickets via the web portal. I've tested this from multiple source email systems (MS and Google). There's no errors in the OSTicket log and nothing of consequence in the server logs.

The following errors are displayed in the ticket:

Server Information
osTicket Version v1.15.6 (1a64b84)
— v1.15.8 is available
Web Server Software Apache/2.4.41 (Ubuntu)
MySQL Version 8.0.29
PHP Version 7.4.3
PHP Extensions
gdlib Used for image manipulation and PDF printing
imap Used for email fetching
xml XML API
xml-dom Used for HTML email processing
json Improves performance creating and processing JSON
mbstring Highly recommended for non western european language content
phar Highly recommended for plugins and language packs
intl Highly recommended for non western european language content
fileinfo Used to detect file types for uploads
zip Used for ticket and task exporting
APCu Improves overall performance
Zend Opcache Improves overall performance
PHP Settings
cgi.fix_pathinfo "1" is recommended if AJAX is not working
date.timezone America/Chicago

I'm at a loss. This only occurs with the new email address being added. All settings are the same as the default address.

Any suggestions?