Full Featured Email Transfer Class for PHP. PHPMailer features:

* Supports emails digitally signed with S/MIME encryption!
* Supports emails with multiple TOs, CCs, BCCs and REPLY-TOs
* Works on any platform.
* Supports Text & HTML emails.
* Embedded image support.
* Multipart/alternative emails for mail clients that do not read
  HTML email.
* Flexible debugging.
* Custom mail headers.
* Redundant SMTP servers.
* Support for 8bit, base64, binary, and quoted-printable encoding.
* Word wrap.
* Multiple fs, string, and binary attachments (those from database,
  string, etc).
* SMTP authentication.
* Tested on multiple SMTP servers: Sendmail, qmail, Postfix, Gmail,
  Imail, Exchange, etc.
* Good documentation, many examples included in download.
* It's swift, small, and simple.