When using IIS7 with PHP 5.2.5 with the FastCGIModule, the mail() function returns the following error message when trying to use anything but a plain email address (ex. test@xxxxxxxx) in the From or To headers: PHP Warning: mail() [function.mail]: SMTP server response: 501 Incorrect Address Format If you use a plain email address it works fine. An example of what causes this problem is as follows: Test <test@xxxxxxxx> The problem is that PHP is formatting the header incorrectly but adding additional < and > tags around the entire address. This is illustrated in this excerpt from my mail server log: 16:28:05.79 5 SMTPI-39353([XXX.XXX.XXX.XXX]) inp: MAIL FROM:<Test <test@xxxxxxxx>> With a plain email address, it still adds the < and > tags, but it works. Here is an example of that from the mail server log: 16:28:21.72 5 SMTPI-39408([XXX.XXX.XXX.XXX]) inp: MAIL FROM:<test@xxxxxxxx> Also, this same behavior was reported in Bug #28038 but I have confirmed that this is error does not occurs when using this same PHP version in CGI mode with IIS7. That tells me this bug was fixed, but has reoccured in 5.2.5 with FastCGI. Reproduce code: --------------- <?php $To = "dan@xxxxxxxxxxx"; $Subject = "Test"; $Body = "Test"; $Headers = "From: Test User <test@xxxxxxxx>" . "\r\n"; mail($To, $Subject, $Body, $Headers); print "mail sent!"; ?> Expected result: ---------------- True result Actual result: -------------- PHP Warning: mail() [function.mail]: SMTP server response: 501 Incorrect Address Format -- PHP Windows Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php