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