url in e-mail being changed

I have some PHP code which I use to send out about a thousand e-mails for a survey. All of the test e-mails work. All of the e-mails sent to my colleagues and myself as part of the mass e-mailing work. But one line in the e-mail is being changed for the real recipients. I see that the character string "=10" (the quotes are not in the actual string) is being stripped and replaced by a blank space, or a square, or perhaps other characters as well. All recipients have e-mail addresses at the same university.

The code used to send out the e-mail uses the PHP mail command. Within the text of the e-mail is:

$mtext="http://.../survey.cgi?sid=".$alias."&ins=".$instcode."\n\n";

where $alias is a 7 digit integer which begins with "10" and so the url which is created contains the string "=10".

This code has been used in the past, with $alias starting with the same 2 digits, but sent to recipients at different universities. We never saw this problem in those cases. Does anybody know for certain what is causing this problem? I was told it is possibly a problem with the "quoted-printable" email encoding scheme. Is there something which I can do (perhaps I should just use $alias values greater than 1099999) to avoid this happening again? Or ar there other character strings besides "=10" which can potentially cause problems?

never heard about such thing. you can try to bypass it by adding some letter before the alias number, for example:

then in survey.php check if the "sid" value begin with letter and if so, trim that first letter.

Sounds like the 10 is being picked up as maybe chr(10). No idea why it would be though. You may want to try using the urlencode and/or htmlentities methods on the string/variables.