email's contains = symbol is replaced with some characters in gmail/outlook

I am sending automated mail which is in html format. I am providing a link in the mail which point towards url with equal(=) symbol. for eg: http://mail.com?hel开发者_如何学Clo=10_world this url is replaced with http://mail.com?hello%10_world, that is =symbol is replaced with % symbol in gmail/outlook.

Am i missing some thing???

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The email is using quoted-printable, so the code =10 represents the character with character code 10, i.e. Line Feed (LF). When the line feed character is found in the URL, it has to be URL encoded to make a link out of it, so it's encoded using the sequence %10.

So, it's not the = that is replaced by %, it's the =10 that is decoded as LF and then encoded as %10.

To put a = character in quoted printable you need to escape it as =3D.