E-Mail delivery can be invoked by issuing the command "sendmail -q". For those who are interested in what sendmail actually does, "sendmail -q -v" will give a more verbose version of the delivery process.
It is very convenient to automate the process of e-mail delivery. A tool commonly used for this process is cron.
Edit your crontab:
Add lines of the form:
05 18-23,0-7 * * Mon,Tue,Wed,Thu,Fri /usr/sbin/sendmail -q 05 * * * Sat,Sun /usr/sbin/sendmail -q
Please refer to the crontab man page (available through "man 5 \ crontab") for further information. I think the format is pretty obvious. The example crontab entries shown above send e-mail (if, and only if, e-mail is available from the queue) 5 minutes after an hour on weekdays, starting at 6:05 pm, and stopping at 7:05 am. On weekends, e-mail is delivered 5 minutes after an hour, starting at 12:05 pm on Saturday, and stopping 11:05 pm on Sunday.
As a dial-on-demand user, it is sometimes desirable to have your system collect your e-mail via the POP3 protocol at certain times of the day. You could therefore add an entry similar to the following to your crontab:
0 21 * * * popclient -3 -u <your pop3 user name goes here> -p <put your password here> -o /var/spool/mail/<the user on your system that should receive the collected e-mail> <mailhost.somedomain.com>
Of course, this should all go on a single line.
Then, save the file and leave the editor. The crontab should now be installed.