Email backups and shadowing
The below is of interest only to people whose damtp account was created prior to Michealmas Term 2005 and who are still using the damtp email system. If you use Hermes and you need some accidently deleted email restored, you need to email help-desk@ucs.cam.ac.uk.
Email Backups
Your mail inbox is backed up onto tape approximately once every 10 days and then kept for approximately 100 days until the tape is re-used.
Note: As we no longer do incremental backups of mail spools, we no longer warn people when their inbox is over 10Mb. Large mailboxes can cause mail to run slowly for you and too many large inboxes could fill the disk the inboxes are held on, to check the state of this disk run
df /var/spool/mail
Mail stored in mail folders in your home directory is backed up (both full and incremental) when your home directory is backed up.
Email Shadowing
To guard against accidental loss of an email message before it has been backed up, a shadow copy is saved in a system directory on the mailserver. This does not use any of your disk space quota or add to your mailbox size.
If a message is accidently deleted, a Computer Officer can retrieve the shadow copy for you and store it in your mail folder. This safeguards newly-delivered email which is lost before the tape backup runs.
Note that email which is forwarded to an external address by means of the system alias file maintained by the Computer Officers is not shadowed.
How long is shadowed email kept for
Currently shadowed email is kept for 12 weeks.
Opting out of Shadowing
If you do not wish to have shadow copies made of your email, you can opt out: simply create a file in your home directory called .noshadow and put your mail filtering commands in this.
A .noshadow file takes the same commands as a .forward file.
If you don't want any of your mail to be shadowed, use exim's save command in your .noshadow file to filter all your email into a folder other than your inbox. For example:
seen save mail/mymail
You can also choose to have some of your email shadowed and some not shadowed by using both a .noshadow file and a .forward file. For example you may wish all mail from a selected sender to be forwarded off-site and not shadowed, but the rest of your email to be delivered locally and shadowed.
To achieve this put the commands to forward email off-site in your .noshadow file, and put other filtering commands in your .forward file. Alternatively omit the .forward file to have mail delivered to your system inbox.
The system will process your .noshadow file, then if it hasn't dealt with an email (eg forwarded it off site, filtered it, or removed it) it will shadow the email and then process it with your .forward file. If it can't process it with your .forward file it will then deliver the email to your inbox.
If you are using both a .noshadow file and a .forward file bear in mind that the .noshadow file will always be processed first.
Users who are leaving damtp should give their forwarding address to a Computer Officer for inclusion in the system alias file. Then a copy of your email will not be kept on a system you no longer have access to. If you prefer we can cancel your email address instead.
Useful Links
Please email any suggestions, corrections, broken links, or errors to itweb [itweb@damtp.cam.ac.uk]