If you have a static IP address, you should not need to adjust anything from the defaults. Set your host name to your assigned Internet name and sendmail will do the rest.
If you have a dynamically assigned IP number and use a dialup PPP connection to the Internet, you will probably have a mailbox on your ISPs mail server. Let's assume your ISP's domain is example.net, and that your user name is user, you have called your machine bsd.home, and your ISP has told you that you may use relay.example.net as a mail relay.
In order to retrieve mail from your mailbox, you must install a retrieval agent. The fetchmail utility is a good choice as it supports many different protocols. This program is available as a package or from the Ports Collection (mail/fetchmail). Usually, your ISP will provide POP. If you are using user PPP, you can automatically fetch your mail when an Internet connection is established with the following entry in /etc/ppp/ppp.linkup:
MYADDR: !bg su user -c fetchmail
If you are using sendmail (as shown below) to deliver mail to non-local accounts, you probably want to have sendmail process your mailqueue as soon as your Internet connection is established. To do this, put this command after the fetchmail command in /etc/ppp/ppp.linkup:
!bg su user -c "sendmail -q"
Assume that you have an account for user on bsd.home. In the home directory of user on bsd.home, create a .fetchmailrc file:
poll example.net protocol pop3 fetchall pass MySecret
This file should not be readable by anyone except user as it contains the password MySecret.
In order to send mail with the correct from: header, you must
tell sendmail to use
<firstname.lastname@example.org> rather than
<email@example.com>. You may also wish to tell sendmail to send all mail via relay.example.net, allowing quicker mail transmission.
The following .mc file should suffice:
VERSIONID(`bsd.home.mc version 1.0') OSTYPE(bsd4.4)dnl FEATURE(nouucp)dnl MAILER(local)dnl MAILER(smtp)dnl Cwlocalhost Cwbsd.home MASQUERADE_AS(`example.net')dnl FEATURE(allmasquerade)dnl FEATURE(masquerade_envelope)dnl FEATURE(nocanonify)dnl FEATURE(nodns)dnl define(`SMART_HOST', `relay.example.net') Dmbsd.home define(`confDOMAIN_NAME',`bsd.home')dnl define(`confDELIVERY_MODE',`deferred')dnl
Refer to the previous section for details of how to turn this .mc file into a sendmail.cf file. Also, do not forget to restart sendmail after updating sendmail.cf.