Here is, I believe, the customer's final response to the rest of the questions:
Here is the customer's reply. Thanks for looking into this:
Thank you so much. I will work with the customer to get the answers to your questions.
We are going to look into the issue you are reporting.
When you are sending from your Mac, are you sending specifically from the Mac Mail app?
Are you having this issue with all file formats (.pdf, .docx, jpeg, etc.) or just one document type, specifically?
If you log into your mail provider's website (gmail, yahoo, etc.) from the Safari browser, and attach a document, does it show up in the @PrintByXerox documents list?
Mobile Print Admin
It seems I didn't explain myself fully. It seems more like the Xerox server is ignoring the attachment. If the customer sends the same attachment from her desktop to a phone, the attachment arrives intact; then, if forwarded to email@example.com, the attachment appears in the list of documents on the copier interface. If the customer sends the attachment to firstname.lastname@example.org, the attachment never appears in the list of documents on the copier interface, although the email does. We tried this using two different phones: same result. So the attachment is being sent.
So, if the issue is already discovered to be that Mac Mail isn't sending an attachment, have you contacted Apple?
The Xerox service can't print something it never got. If you send the same thing to your phone instead of the @printbyxerox account do you get the attachment? If yes, how is it different than when you send from your phone to your Mac?
We are trying to use email@example.com on our C8030 recently acquired. If I send an email with attachment from a Mac desktop using Mail, the attachment does not appear in the list of documents received by @printbyxerox. But if I forward the same email and attachment from my phone, everything appears and prints without a problem. When @printbyxerox sends me the acknowledgement message, the attachment is not listed if I send from the Mac Mail application. But if I send from any other client, the message and attachments are listed in the acknowledgement message. Is there a fix for this? Mac OS 10.12.6, Mail 10.3(3273)