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=pod
=head1 swaks - Recipes for use
Because swaks is a very flexible tool it can be hard to fully grasp what it can do (and few people want or need to). However, I have used swaks in interesting ways, and others have done the same and shared them with me. I hate for these interesting ideas go to waste, so I am including them in this file.
=head1 Simple address verifier
I have had the following in my kshrc for years:
=over 4
alias vrfy='swaks -q rcpt -t'
=back
This allows you to quickly ask a mail server whether a recipient is valid (depending on how the mail server is configured, of course). Example output:
=over 4
g3 0 /home/jj33 > vrfy proj-swaks@jetmore.org
=== Trying mx2.balanced.spacey.mail.dreamhost.com:25...
=== Connected to mx2.balanced.spacey.mail.dreamhost.com.
<- 220 spaceymail-mx3.g.dreamhost.com ESMTP
-> EHLO g3.jetmore.net
<- 250-spaceymail-mx3.g.dreamhost.com
<- 250-PIPELINING
<- 250-SIZE 40960000
<- 250-ETRN
<- 250-STARTTLS
<- 250 8BITMIME
-> MAIL FROM:<jj33@g3.jetmore.net>
<- 250 Ok
-> RCPT TO:<proj-swaks@jetmore.org>
<- 250 Ok
-> QUIT
<- 221 Bye
g3 0 /home/jj33 >
=back
This is a valid email (the mail server returned 250 in response to my RCPT request). This is fairly verbose though. Note the "0" in my command prompt is the exit status of the last command ($?). Since swaks tries to be good about setting a useful return value, I could make vrfy totally silent:
=over 4
g3 0 /home/jj33 > alias vrfy='swaks -q rcpt --silent 3 -t'
g3 0 /home/jj33 > vrfy proj-foobar@jetmore.org
g3 24 /home/jj33 > vrfy proj-swaks@jetmore.org
g3 0 /home/jj33 >
=back
As you can see by the $? output, proj-foobar is not a valid address and proj-swaks is.
This works well if you use $? in your command prompt, but if not it is less useful. Also, it loses potentially useful information the mail server might provide when rejecting an address. To get around this, try using --silent 2, which prints only errors. Now you can expect no output to mean the mail was valid, and any other output to mean an error occurred:
=over 4
g3 0 /home/jj33 > PS1=$HOST' $PWD > '
g3 /home/jj33 > alias vrfy='swaks -q rcpt --silent 2 -t'
g3 /home/jj33 > vrfy proj-foobar@jetmore.org
<** 550 <proj-foobar@jetmore.org>: Recipient address rejected: User unknown in virtual alias table
g3 /home/jj33 > vrfy proj-swaks@jetmore.org
g3 /home/jj33 >
=back
=head1 Stress-testing an SMTP server
I've received a couple of different requests and a couple of different patches over the years to add functionality to have swaks fork and send a bunch of emails to a single address. I may still add this functionality some day, but I still feel pretty strongly that ultimately swaks core is a single transaction. Forking multiple swaks seems just outside the scope of the tool.
However, this does seem to be something people want to do. To that end, here is a quick-and-dirty shell script that is (almost) a drop in replacement for swaks:
=over 4
#!
=back
=cut
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