Re-route is a startup (a scary word these days) that forwards email from your old ISP to your new ISP. This can be done while your old ISP subscription is still valid (we retrieve your email and send it to the new ISP you are transitioning to).

The backend code that processes retrieved email (the address correction, change-of-address notice generation and SMTP communication) was all recently re-done in Tcl (relying heavily upon tcllib's mime and smtp libraries). The Tcl code consists of 3 long running processes (they only go down when we take the whole system down) that handle anywhere between 10,000 -> 20,000 emails per day and sends out double that amount via a local SMTP daemon. The Tcl code uses Berkeley DB persistent/transactional queues for communication and Postgres for updating customer info.

We were going to rewrite the Tcl prototype in C/C++... but why bother? :-)

-- [Todd Coram]


----
Cool!  Nice description, Todd.

e-mail remains the original killer app, and Tcl certainly can do e-mail.

-----
''An update'':

We just deployed an email forwarding system (with automatic change of address notification) for a certain wireless phone company (starting with the letter '''V''') to migrate their customer's email service to a certain ISP/Mail provider known to some by the initials '''MS'''. It's 
QMail + 1 C++ app + a bunch of Tcl handling 100,000+ emails per day. Its all tied together by a Tuplespace implemented in Tcl and Metakit. Its spread out over 5 machines and its all controlled by Tcl.  If there is any doubt about using Tcl for long running code: Tcl is running 24x7 with no glitches and no leaks. Kids, don't try this at home (with C++).

-- [Todd Coram]