email class - how to set envelope-from

[eluser]Unknown[/eluser]
A customer of mine has an email server configured to generate an error message when the 'To' and 'Envelope-From' addresses are the same.

Codeigniter, it appears, sets envelope-from to the same as the 'From' address.

If I could set the envelope-from address to something else, I could try to confirm that this is my problem.

How do I go about setting the envelope-from address?

[eluser]CroNiX[/eluser]
There isn't a setting for it afaik. You'd have to extend the email class or just use regular php mail().