AsterFax is an email to Fax gateway for Asterisk.
You can download AsterFax at: Link
The newly released Beta 6 introduces a host of new features including:
The body of an email is now used as a cover page to any file attachments.
AsterFax now attempts to identify any configuration problems and provide a plain english explaination on how to fix them.
Faxes can now be automatically archived to a mailbox
A delivery receipt is now sent on the successful transmission of a fax.
Expanded set of supported file attachments
And many more.
Oh and of course lots of bug fixes too