Paypal Standard Problem Redirect and mails error!

[Studio 42]

If the website run fine on another server, i think that you have some restriction or server use a proxy, cache(cloud) or similar issue.

[Jörgen]

Is this maybe your mailserver resending the mail? Check smtp settings
Regards
Jörgen @ Kreativ Fotografi

[Worklive]

Is this maybe your mailserver resending the mail? Check smtp settings
Regards
Jörgen @ Kreativ Fotografi

Are these ok?

Setting SMTP: http://newbiosrl.altervista.org/paypal/settings-mail.png

[Studio 42]

Check with the "Send test mail" button (see in your screenshot.
If the test is good, then use same email in your shop settings

[Jörgen]

I had trouble using PHP mail, switched to SMTP and that workes much better.

regards

Jörgen @ Kreativ Fotografi