I get emails like that too, from time to time.
The gibberish is usually in "base-64" encoding, which is normally used
as a way to encode binary data into non-binary text where it can be
emailed. Usually you don't see it that way because the header and
other stuff in the email message have the right information to tell
your email reader that it is in base-64 and needs to be decoded.
I think you occasionally see messages displayed like that because the
sender's email lacks some of the required tags that are supposed to be
there to identify it as base-64. Some email readers recognize it
anyway and do decode it (so they look normal), but others do not.
Oops - I just noticed you are seeing these blocks within the email
header itself. That is something I haven't seen, which is to say I
never saw it on those occasions when I looked at the headers. It
might explain why your subject line appears blank; your email reader
may stop interpreting the header at that point.
When I get those emails with base-64 encoded gibberish within the
emails, most of them are on another email group to which I belong, not
a Yahoogroup, and I think don't come from Yahoo mail either. But what
I've seen might be different than what you described.
Andy
