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Email Service
CPTE 433John Beckett
The Fundamentals
• Reliable• Scalable
– Issue is speed• Flexible
– Clients, locations• Growing issue: Spam control• Growing issue: Storage
Privacy
• Fit with your organization’s culture.• Clearly state policy.• Distribute policy; get signatures.• Use policy as a statement of
maximum intrusion, not minimum.• Keep incidentally-acquired
knowledge secret.
Namespaces
• See previous chapter.• Two issues:
– Recognition of who this is– Non-duplication
• Special problem for colleges: marriage
• What about when people move around?– You might have an alias list pointing to
people with specific responsibilities, e.g. eclasshelp.
Reliability
• Upgrade plans for email must be laid more carefully than those for other services.
• Better to hold mail at bay than to lose it.– Simplest method: unplug the Ethernet
jack or take down the service
Aspects
• Mail Transport– This is done by the equipment designated to the
right of the “@”.– In DNS, this is the “MX” record.
• Delivery– GUI / non-GUI client– Webmail/OWA/SquirrelMail (is both client and
server)– Consider protocols used: POP3 and IMAP4
• List Processing– Big question is, who can send to which list?
Fading Technologies
• MTA on a client machine– May wish to deny this in your firewall
• Proprietary protocols – CCMail– CompuServe
Emerging Technologies
• Encryption*• Non-repudiation*• Spam control
* This is a reason SAU has migrated from Procmail to Microsoft Exchange Server.
Automation
• Setting up the account should be part of the process of signing up for a job.
• List administration should be automated either ex officio or at user’s election.
• What about when people leave? – No forwarding outside.– Either refuse the mail or send it to their
replacement.– At SAU: When does a person really
leave?
Monitoring
• Watch disk space consumption. That will tell you:– If someone is being attacked.– If you are not filtering SPAM properly.– If someone is using email to do something
that should be done through another process.
• Watch the bandwidth. – Positive trend: more bandwidth on
connection– Negative trend: SPAM
Redundancy
• Keep mail flowing in and out of the site even if one mail exchanger goes down.
Scaling
• Move other services off the mail machine.
• Separate mail functions such as WebMail client and MTA.
• Get a bigger machine.• Do a better job of SPAM control.• Provide alternate means or hosts for
troublesome emails – Art department example.
Security
• Your mail system will be a target.• If you count SPAM, it’s a target every
second of the day!• Watch the resources: disk I/O, disk
space, bandwidth.• Of course, stay updated.
Backups
• Do you want to back up local folders?– Yes: You have to be able to recover it if it
breaks.– Yes: You may be required to recover deleted
emails.– No: That’s not your job.– No: Leaves unnecessary records that could
be used by a prosecutorial opponent.• Backup policy should be clearly stated
and understood by all.
High-Volume Lists
• You may want to split the list into multiple sub-lists for simultaneous processing.
• GC example: From 4 hours to 30 minutes on a 30,000-person list.
Consider Off-Site
• Gmail.com is happy to do it (free!)