Last update: 05.01.2005
SendmailSendmail is a so-called MTA (Mail Transfer Agent) like postfix, qmail or exim. I'm not really sure, but AFAIK sendmail is the oldest MTA. Don't confuse MTA and MUA. MTAs are the server programs that receive mails and send them to other MTAs or deliver it local (in your mailbox). MUA are the mail programs you know, like kmail, Netscape/Mozilla Messenger or even (uhaaa) Outlook.
The best way to configure sendmail is via m4. When you install sendmail you usual get a directory called cf. The various locations I know are:
You will find a quite good README in these directories. It covers almost everything you have to know about sendmail configuration. To generate a new configuration go to the cf directory beyond the above mentioned directories (yes, /usr/newconfig/etc/mail/cf/cf on HP-UX and so on) an create an mc file. I call this file normally sendmail.mc. When you have created the sendmail.mc (see the sendmail.mc part) do the following:
m4 ../m4/cf.m4 sendmail.mc > sendmail.cf cp sendmail.cf /etc/mail ln -s /etc/mail/sendmail.cf /etc/sendmail.cf # Only once needed cp sendmail.cf /etc/mail/.sendmail.cf
As you can see, I usually put the sendmail.cf in /etc/mail and make a link from /etc/sendmail.cf to /etc/mail/sendmail.cf. These are the two locations where you usual find the sendmail.cf (and the sendmail binary usual look for).
The .sendmail.cf isn't really necessary. I do this to have a copy of the generated file. This is useful if you are not the only person who has root. If the other person is known for editing the sendmail.cf you just have to do a diff to check what he has done.
Important: Always recreate your sendmail.cf when updating sendmail. It is possible, that some of the macros have been changed.