POP3 messages: '=' always followed by '3D'?

[Steve Canfield]

I'm using poplib to retrieve email messages.  Whenever the text of the
message contains an equals sign, it is always followed by '3D'.  Why
is this?  To get the original text, do I have to do a
search-and-replace operation on every line to convert '=3D' to '='?

For example, if the message contains this:
  <abc def='ghi'>
it will be retrieved as:
  <abc def=3D'ghi'>

Am I missing something painfully obvious here?  Any suggestions for a
easy and fast way to fix this?

-steve