Strange email issue - Any ideas please?

[Frankc]

A client (my brother) always send PDF invoices from Pastel via his email account hosted on a cPanel server.

About 2 months ago such PDF invoices is unreadable with I/O error but if send via other smtp server the same PDF invoice don't have any problem.

I tried to send PDF invoice from server (My own billing system) without any problem.

If his smtp is set to the cpanel server smtp (maildomain.com or IP address) then it cannot be opened but if changed to his internet connection smtp (one of our biggest cellphone companies) then it can be opened.

So far as I know NOTHING server side can cause this and my reasoning is that the document is somehow changed "en-route". (There is a few extra bits in the unable to open PDF document)

Any ideas perhaps please guys?

(I am by the way deaf and have the hosting business for almost 10 years so I am not too stupid and REALLY relay very much on email to work 100%)

 

[Frankc]

When try to open the PDF document.

"There as an error processing a page. A file I/O error has occurred."

If the PDF is send to me via outside smtp I can read it, if I forward it via my own smtp to email address on the same server as well as an outside email address and both opened.

It's just if SEND by Pastel VIA the cpanel's server smtp that the PDF file become corrupt somehow. (If send via other smtp it's not corrupt and send back and forth in different ways thru the cpanel server don't effect the PDF document)

 

[cPanelMichael]

Hello

Do you notice any specific errors related to this message in the /var/log/exim_mainlog file? Try searching for it via:

# exigrep [email protected] /var/log/exim_mainlog

Also, have you tried viewing the message via Webmail to rule out any issues with your email client or locally installed Antivirus application?

Thank you.