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Next: Accessing the Mailserver Up: Special Chapter: Mail Issues Previous: AFSmail and the MailServer

Mailforwarding - Make Sure You Do Not ``Lose'' Mail


Many of you have accounts on several computers at CERN but not all of you may be aware of the fact that this also means there is a valid mailbox address that goes with your home directory on these computers. For example, if you have a home directory in AFS you have a mailbox addressed as

which is valid on all machines that are AFS clients and have their users' home directories stored on AFS. You may still have an account on say, CERNVM, VXCERN, or dxcern, and a new one on the MailServer. How do you make sure that

you collect all mail that is sent to one of your mailboxes in one place,

you avoid that mail goes back to the sender because you have arranged by bad forwarding requests that the message bounces between two of your valid mailboxes?

Here is a proposal for attacking the problem in a systematic way:

Make a list of all your valid computer accounts (use e.g. xwho).

Decide on which computer(s) you want to read your mail.

Identify the computer on which you want your mail to be delivered. This computer is your ``mail target''.

If you want to (or have to) read your mail independently of where you are logged in, e.g. because you are a user of a cluster of machines, for example cernsp, use the MailServer ( as your mail target.

On all other computers where you have an account you should activate mailforwarding using the address:


for example:

if your ``mail target'' is the MailServer and you own the MailServer account ``fred''

No forwarding should ever be established on your mail target except in the case of the mandatory AFS forward (see below). Please be aware of the fact that mail will be returned to the sender if your mail target, e.g. your personal workstation is unreachable (e.g. switched off because you are on vacation) for more than two days.

If you currently have your mail delivered in your AFS mailbox, the appropriate forward has already been set up when your AFS account was registered. To get all your mail delivered into your AFS mailbox make sure that mailforwarding is activated on all your non-AFS accounts on other computers, even on the MailServer if you have an account there. The mailbox address to be used for forwarding is:

Make sure that your entry in the Electronic Mail DIRectory EMDIR is identical with your mailbox address used for forwarding.

In principle you should never have a forward defined on the computer where you want your mail to be delivered. One exception to this rule is the activation of an automatic mail answering mechanism, e.g. telling people that you are absent and they should send mail to your deputy/secretary/colleague in case of urgent problems. Another one is the mandatory forward in your AFS account which enables delivery to your AFS mailbox.

Unfortunately the way in which a mail forward is installed varies from computer to computer. However CERNVM, VXCERN, dxcern, cernsp, hpplus, the workgroup servers and the MailServer all have a program called ``mailfwd'' installed that helps you to verify the current state of forwarding and to install new or add to old forwarding directives, for example:

mailfwd -q

will tell you where your mail is currently forwarded to, and:


will make all your mail received on the host on which you are executing this command go to fred's mailbox on the mail server. For details on other options of mailfwd please consult the man pages.

Your ``generic'' address (see the article 3.3, ``Obvious Names, Generic Addresses and Preferred Email Addresses'', in this issue) which has the form

can be used as forwarding directive provided your EMDIR address points to the host where you want to read your mail. However you should never put this address itself as EMDIR address nor use it as forwarding address on the host your EMDIR address points to.

As a general rule make sure that you do not create the situation that host A redirects your mail to host B and host B redirects your mail to host A (or variants of this where even more hosts join the game). The result of this ping-pong is that the message will never reach you. It is returned to the sender when a maximum number of hops is exceeded and it might take some time before you are aware that you don't receive any mail and start to investigate.

next up previous
Next: Accessing the Mailserver Up: Special Chapter: Mail Issues Previous: AFSmail and the MailServer

Michel Goossens
CN Division
Tel. 3363
Wed Mar 13 07:42:40 MET 1996