7. POP mail

This section also concerns IMAP, not very different from POP.

7.1 History

On a workstation network, mail has always been a problem:

• Either you use "user@computer.foo.com" with problems when "computer" is down, making your network known to the people outside, having different addresses for a same person switching to another computer, ...
• Either you take a mail hub, "mailhost.foo.com" with rules for rewriting, so every user seems to post from the same address, even if they are on different computers.

But in that case, how can user read their mail ?

Using a rsh with elm ? :-)

It would overload our mail hub ! One method was forwarding or UUCP, smtp, etc. but it's too complicated.

Then came POP/IMAP, both with security problems at the beginning, now fixed using ssh on new versions) : a mail program has sometimes to be set locally (like qmail, smail or vmail if, for example, you use elm, but mozilla will avoid that !) however, getting and sending Email is simpler.

7.2 Getting mail

Here come POP's main drawbacks : the password is sent as a clear text on the network, and some mail readers just don't know POP : you must choose a POP-aware mailer, like Pine, Emacs, Netscape, Mutt ...

Password problem can be solved creating a crypted "channel" to have POP on it or using APOP or RPOP extensions. The mail reader problem can be solved either by changing mail reader (mozilla is POP ready, as are Emacs and pine) or by using a POP "mail sucker" with a local mail program.

Here're some pop programs worth trying :

• gwpop (a Good Way to POP) is very protected since it creates a crypted "channel" and puts mail directly in the "spool" ; however, it depends on Perl.
• popclient, simple to use : For example if your login is john and your password PrettySecret, you will run :

  $ popclient -3 -v mail.acme.net -u john -p "PrettySecret" -k -o JOHN-INET-MAIL
  

• fetchmail, which is actively supported and incredibly simple to use : it is configured in ~/.fetchmailrc, so you only need to run fetchmail when you want to retrive your mail. Here's my .fetchmailrc :

  poll mail.server protocol pop3:
          forcecr
          password PrettySecret;
  

  Please note forcecr option is needed to use fetchmail with qmail which strictly respects RFCs.

7.3 Sending mail

For this, you must use smtp-aware mail software, like qmail, smail, vmail or mozilla (this one does everything : mail reader, POP receive, smtp send !)

Go to one of the previous sections to install and configure the one you like best. Then, will you will reach "Testing", try to send some mail to a local account on the mail hub.

7.4 Reading mail

If your program doesn't do everything itself, you can install elm, pgp, mush, pine ... many good programs are freely available for linux platforms !

7.5 Testing

To check your mail server has pop, try :

$ telnet mailhost 110

If it works, you will get something like "OK Pop server (...) starting" : type "quit" !

To install a ssh crypted "channel", first test your mail server typing :

$ ssh mailhost date

If you get the date, you should be OK. Please note ssh will not ask for a password, therefore you must create a ".shosts" file on the mail server, containing client's name. To test ssh port redirection (which gwpop uses), type :

$ ssh -n -f -L 12314:localhost:110 mailhost sleep 30

then

$ telnet localhost 12314

Then will you hopefully see mail hub's pop banner. If you don't use ssh, don't forget to comment out $ssh on gwpop script. To check whether procmail is running, try "procmail -v"

7.6 Using

Now you can edit gwpop Perl script to check everything is ok, then run gwpop :

$ gwpop -v your-username
POP password on mailhost: yoursecretpasword

If gwpop "error messages" are normal, the mail from mail hub will be downloaded to your local machine wherever you told gwpop to put it. (please test with some mail !).

You can also use gwpop as a daemon :

$ gwpop -d $HOME/tmp your-username

gwpop messages are then sent to syslog and gwpop will run endlessly ; a "HUP" signal will force gwpop to get your mail.

You can get POP software here used on :

ftp://ftp.pasteur.fr/pub/Network/gwpop
ftp://ftp.informatik.rwth-aachen.de/pub/packages/procmail
http://www.cs.hut.fi/ssh/