POP/IMAP service

Usage of the cc:Mail system  very quickly started to exceed the capacity of the system. Its shared database for each post-office proved to be a security issue that could only be alleviated by having lots of post-offices. Unfortunately the gateways for linking them together expected low volumes of inter-postoffice mail and worked on a polling principle. this does not work for scaling systems so a re-design was needed

Courier IMAP server

qmail SMTP server

Outcome: subseconnd deliveries, users could choose their own standard-compliant email program and happiness ensued.

cc:Mail

With the shift of the Academic Computing Service to pc-based in the early 1990’s we had to replace GMAIL. The University obtained a license for cc:Mail very cheaply, and it had won numerous awards. Once we started deploying it we realized some of the significant issues, largely around the shared-database model which would not survive an attack be a malicious program. this was tried to mitigate by lots of post-offices (two per department), but this hit other scaling issues.

Unfortunately we realized this when we got an award for having more than 10,000 users in it. The SMTP gateway would loose message sif there was any database corruption. In one of major feats of programming wrote a SMTP gateway from scratch over the weekend. Looking back, we could probably have used this to link the post-offices together but really the scaling issues and database corruption was a big problem that would only have partially solved.

Mail routing

Until the Prime-9955 computers were replaced mail routing was done by the coloured book software running on them. A parallel system running on a SUN 4/330 and HP8000-735 coped with X.400 based email until the UK academic community abandoned the transition to ISO protocols and switched to TCP/IP and SMTP mail. Finally we switched to qmail because the use of Maildir allowed us to scale the IMAP/POP message stores horizontally and cross-mount them using NFS without worrying about locking.

Routing and delivery of mail have always been handled separately on systems I have managed. this had allowed various components to be swapped out without breaking the whole infrastructure. Also, running a central mail routing service allowed departments to hand email off to those systems for routing without having to open their internal mail gateways up to the Internet. This allowed departments to chose to run their own email delivery system if the desired (a couple ran Lotus notes for example)

Theme: I like to enable the use of central services that enable academic departments to do what is important to them.

Software I have used for mail routing includes Sendmail (SMTP and greybook); PP (part of the isode stack); qmail; postfix

Glasgow Mail

This was the first real email system I installed on the University Prime 9955 computers; it replaced the very basic email functionality offered using greybook mail and the native mail tools.

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