POP3 uses a similar format to HTTP POST, and message content is typically encoded in this way. (The transfer encoding header will tell you, it is "quoted-printable" – see
Wikipedia[
^].) It is a simple job to decode such strings (the two characters after an = give you a byte code).
Remember when reading emails that you also have to deal with multi-part messages and MIME-encoded sections (for example images or attachments).