Originally posted by: Wouter Liefting
What AIX program are you using to sent the e-mail? Most likely the program you are using is not setting the mime-type (also known as Content-type) correctly.
You may want to compare the source of the two e-mails (the working one and the non-working one) with each other to see what's going on. In the normal web-based gmail there's a button "Show Original" - but if you do e-mail in a different program or web client there will be similar tools somewhere. Anyway, this will show you the e-mail as it was setup and transferred. There's a couple things to look for.
1. In the main header there will be a line like this:
Content-Type: multipart/alternative; boundary=001a113372b8c7f0d304f7b10bb1
or
Content-Type: multipart/mixed; boundary="----=_NextPart_000_0048_01CF5A45.3BDDD230"
This tells your mail client that it's a multipart mail, and what the boundary string is.
2. You will then have sections that each start with this:
--001a113372b8c7f0d304f7b10bb1
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
This tells you that anything that follows, until the boundary string is encountered, is plain text. But you can also see stuff like this:
--001a113372b8c7f0d304f7b10bb1
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
...for HTML text
------=_NextPart_000_0048_01CF5A45.3BDDD230
Content-Type: application/vnd.openxmlformats-officedocument.wordprocessingml.document;
name="something.docx"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="something.docx"
... for a .docx attachment
You need to compare the Content-Type fields to each other, and that will probably tell you what your AIX mailer is doing wrong. If your mailer supplies the wrong, or no Content-Type, then the mail client doesn't know what to do with it.