A new version of PHPMailer came out in early June 2008, which works with PHP5, in E_STRICT mode.

http://sourceforge.net/project/showfiles.php?group_id=26031&package_id=252700

Also, among the fixes since 1.7.3 (which is the version we are using, according to the changelog):

• fixed the SendMail security issues (input validation vulnerability)
• added TLS/SSL SMTP support
• added S/MIME functionality (ability to digitally sign emails)
• addressed issue of multibyte characters in subject line and truncating

Full changelog: http://phpmailer.codeworxtech.com/changelog.html