Where does sendmail put the mail when it queues it? The mail queue directory is /var/spool/mqueue. All mail messages become two files, one named dfXXXnnnnn , the other qfXXXnnnnn , where XXX is a three-letter sequence, nnnnn a five-digit sequence. They are used to give every message a unique identifier. The "qf'", or queue control file, contains the e-mail message header and various processing information, and the "df'", or data file, contains the body of the e-mail message. There are other files, but they are of interest only to sendmail.
To see what sendmail is doing, check the file: /var/log/maillog. It is pretty hard to read, but is your only real chance to see what the error might be.
Some of you may log into your local computer with a different name than what you use for your ISP. Fetchmail will obviously get your mail and put it where it belongs, but sendmail needs some special help. Check out the Sendmail-Address_Rewrite Howto. If you have been able to followed this article, this Howto is pretty simple.
Do not be put off if things do not work the first time! I have been using sendmail for 4 years with varying degrees of success. It is a big beast that has evolved greatly over time. Since the vast majority of email on the internet travels via sendmail somewhere along the way, it is worth the time to get it working on your computer.
Final thoughts: We have given you a cookie-cutter recipe for setting up a simple home mail system. Since success usually creates greater interest, here are some places to learn more:
Sendmail Homepage
Fetchmail
Homepage
Procmail Info
Two well know alternatives to sendmail: