I'm getting bounce mails about an invalid mimetype

If you're getting bounce mails about an invalid mime type, this means an email came into the 1Archive system and was rejected.

These emails contain one or more MIME encoded (pdf) files as attachments which differ enough from the accepted standards as to be considered a risk to our systems.

Such files are often viruses or spam, which we actively discourage, and thus cannot accept for delivery. This policy is applied on all our systems and no exceptions can be made so please do not ask.

If you know that the attached file is not a spam or a virus then the problem is because your email client (older versions of Microsoft Outlook, etc.) is broken and cannot send email in the proper format. Unfortunately, due to the levels of viruses which masquerade as invalid attachments, we cannot risk allowing such broken mail through.

Your best chance is to use a different email application, which may have a better MIME encoder. Another solution might be composing the email in another format (e.g. HTML).

When you download such an email as an *.eml file and open it with a text editor like Notepad++ you will find

• Content-Type: application/pdf; name="invoice1.pdf" (this is a well-formed email)
• Content-Type: application/ms-tnef; name="winmail.dat" (this is an erroneous email)