How to upload file from Unix to Microsoft SharePoint URL?

I am attempting to upload a file from a Unix machine to a Microsoft SharePoint URL within a shell script. The SharePoint is setup to accept emails with attachments. When an email with an attachment is sent to the URL, the file is uploaded. I am unable to get the same functionality from within my script using the mailx command.

My attempt:

uuencode $fullPath ${file} | mailx -m -s "Outage Report" $spEmail

My attempt works when sending to a personal email (files are sent as attachments), but the files are not uploaded when using my SharePoint URL.

I have tested the SharePoint URL by mailing from my personal email (via Outlook) and the files are uploaded correctly.

Q: Why am I unable to mail files from the script directly to the SharePoint?

Add content to sites by sending e-mail - Office Support

Thanks,

Matt