Some email recipients get messages with =0D or =3D characters

I have a LAMP web application that emails users. Some users have complained that instead of seeing html email messages, they see weird sequences of chara开发者_开发百科cters such as =0D or =3D. I can't reproduce this bug with any of my email clients : gmail, yahoo mail, hotmail, thunderbird, blackberry or iphone. Does anyone know what's going on and how to fix this?

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This is called quoted printable encoding. Some system that handles the mail while it is being delivered to the recipients that are seeing the offending characters messes up the encoding or the header information about the encoding.

Check whether the encoding you are setting when sending the mail matches what you are writing to the mail and whether that is also what is received by other people.

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When you see something like =3D, what you're seeing is a single character in what's called "quoted-printable" encoding. "=3D" is, in fact, an equal sign. =0D is a Carriage Return (CR), =0A is a Line Feed (LF)

Taken from Not all 'plain-text' is created equal...

The link will provide an in-depth detailed description as to what is going on.