You probably didn't know this, but every email is actually plain text, even RTF emails and HTML emails. It has different sections (e.g. the headers, the body, the attachments), and some of these sections can be encoded. This encoding is a means for putting non-plain text in the plain text email. Base64 is the most common way for attachments to be encoded.
When a client opens an email, it checks all sections, and decodes where necessary. Then it displays all sections as needed.
"The cause of the problems you are encountering while sending the zip.files attached to the emails have been located by our Amos Technical Experts.
The emails are not being blocked, but during storage of the attachment within our Amos database the system is generating errors:
I 20080422 133121 3536 SMTP incoming from 188.8.131.52 T 20080422 133121 3536 EHLO relay1.station12.com T 20080422 133121 3536 MAIL FROM:<email@example.com> T 20080422 133121 3536 RCPT TO:<firstname.lastname@example.org> T 20080422 133134 3536 DATA E 20080422 133134 3536 Unable to save message in database T 20080422 133134 3536 QUIT
This is a bug within our system which needs to be solved by our Amos Development Department".
Joined: Mar 22, 2005
Sounds like the receiving side is aware of the problem, and -hopefully- working to fix it.