It should contain the address of the host where that user??™s mail will ultimately
be delivered.
* Under old versions of sendmail, th evrfy and expn commands are interchangeable. Under V8 sendmail and
other, modern SMTP servers, the two commands differ.
?? In place of specifying port 25, you can use either mail or smtp. These are more mnemonic and easier to
remember (although we ???old timers??? tend to still use 25).
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
13.8 The User??™s ~/.forward File | 503
But beware that the world of email is becoming less friendly for the well-intentioned
administrator. Because EXPN can be used to harvest addresses for spam lists, it is
more and more frequently turned off. If you connect to a site withEXPN turned off,
you will see an error such as the following, instead of the forwarding address you
need:
502 5.7.0 Sorry, we do not allow this operation
If EXPN fails, try finger(1) in its place, which also might fail (another illustration of
the harm caused by spam email).
13.8.2 Forwarding Loops
Because ~/.forward files are under user control, the administrator occasionally needs
to break loops caused by improper use of those files. To illustrate, consider a user
who wishes to have mail delivered on two different machines (call them machines A
and B).
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