The sigfilter mail autosigning programme
Contents
Introduction
sigfilter is a programme that will automatically append a standard personalised signature to mail sent from a local network using the Courier mail transfer agent. It operates in conjunction with SMTP user authentication and a (MySQL) database of user information.
If an organisation is using it's own mail server it will need to prevent relaying by only forwarding (or relaying) mail from machines it trusts. This trust is typically established either by only trusting machines with IP addresses in a particular range or by requesting every user provide authentication via user name and password before mail from them is forwarded.
The range of trusted IP addresses is likely to correspond to the local network block. It may well be 192.168.0.0 - 192.168.255.255 with translation to forwardable IP addresses using NAT technology. [RFC 3022] Using such a scheme it is the machine not the user that is trusted. SMTP user authentication (part of ESMTP - see RFC 4954) provides a mechanism whereby a user wishing to send an e-mail will be challenged to provide a user name and password. It is the responsibility of the mail server to validate the user authentication information. A server such as Courier can use a variety of mechanisms to do this such checking the local user/password file, looking in a database file or talking, using LDAP, to an information server, such as Microsoft's Active Directory. How users are authenticated is of no concern to sigfilter, it inspects the mail looking for the authentication validation indication and then uses the user name to get user information from a database.
sigfilter uses personal information from a database in conjunction with a simple template to construct a personal mail signature that could include information such as telephone/fax numbers, room numbers and job titles. The advantages of creating mail signatures in this way, rather than leaving users to construct their own include :
All signatures will have a standard look. They can include standard organisation information.
Any changes required can be made centrally by changing the database records and/or the signature templates. By changing the template, common information (such as an organisation's address) can be changed on everybody's signature at once.
Correct job titles can be included.