Installation Requisites - IMPORTANT NOTE: Always restart sendmail after altering config files.

 

sendmail	Mail Transfer Agent (Required)
sendmail-cf	MTA Configuration (Required)
mailmain	Mailing List Support/Client
dovecot	IMAP & POP3 or Inbound Mail
squirrelmail	Optional Web based email server(requires MySQL)
spamassassin	Optional Spam Filter

Configure /etc/mail/sendmail.mc

[root@server.domain ~]# nano /etc/mail/sendmail.mc

Now you must configure at minimum, these following options for a proper sendmail.mc config. I will show both the Default option and the reconfigured option. Our Domain will be LinuxTruth.org as I used in my lab environment with the Server's name as Boreas. Our administrators are Jack and our user is Dave from the sales department. Jack the admin also created a username called Sales. Always remember to remove the Delete to New Line (dnl) and know the difference between ` which is below the ESC key and ' which is near the Enter Key if you delete too much of one line.

This is for an Outbound Mail Server

dnl define( `SMART_HOST',`smtp.domain.com')dnl 
define( `SMART_HOST',`smtp.SmtpHostingSite.com')dnl

Revoke SMTP local only isolation and open SMTP Port

dnl Daemon Options (`Port=SMTP,Addr=127.0.0.1, Name=MTA')dnl
Daemon Options (`Port=SMTP, Name=MTA')dnl

Domain Clarification for Email Server.

dnl MASQUERADE_DOMAIN(mydomain.lan)dnl
MASQUERADE_DOMAIN(boreas)dnl
MASQUERADE_DOMAIN(boreas.linuxtruth.org)dnl
MASQUERADE_DOMAIN(linuxtruth.org)dnl

Final touches on Sendmail.mc, make sure these mailer parameter lines do not have dnl before them.

MAILER(smtp)dnl
MAILER(procmail)dnl

Configure /etc/mail/virtusertable with Domain user mailboxes.

[Email Address] *Tab space* [Locally Created User]
jack@linuxtruth.org    jack
dave@linuxtruth.org    dave
sales@linuxtruth.org    sales

Configure /etc/aliases, this is where you can declare and make a distribution list.

User/Group: User
root:    jack
postmaster:    root
daemon:    root
adm:    root
lp:    root
sales:     dave
company:     dave, jack

Now run this command and your server should be functional. Test with another PC. Telnet your Ports to verify connectivity.

[root@linuxtruth.org ~]# /sbin/service sendmail restart

Authenticated Relay Using SSL (Install OpenSSL first)

First, Create an encryption certificate. If you're using Fedora, this directory should be fine. If you don't find this directory. Go ahead and create one.

[root@linuxtruth.org ~]# cd /etc/pki/tls/certs
[root@linuxtruth.org ~]# make filename.pem

Complete the form and fill out as instructed, OU Name does not pertain to any LDAP functions.
Once you've created your certificate, sendmail needs to be instructed to use the certificate. Remove DNL from the lines as instructed and modify others. The first two edited lines inform Sendmail that there will be a certificate encryption, the last 4, define where to find the certificate.

[root@linuxtruth.org ~]# nano /etc/mail/sendmail.mc

dnl This part configures sendmail to use encryption but does not define where the certificate is.dnl
TRUST_AUTH_MECH( `EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
define( `confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl

dnl This next part defines the Certificate's location for each parameter. dnl
define( `confCACERT_PATH', `/etc/pki/tls/certs')dnl
define( `confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl
define( `confSERVER_CERT', `/etc/pki/tls/certs/sendmail.pem')dnl
define( `confSERVER_KEY', `/etc/pki/tls/certs/sendmail.pem')dnl

By this part, I'm sure you're asking yourself, "Well now we're using certificates but aren't we supposed to configure the port assignment? Yes... we are. In fact, use this writing below and overwrite the previous DAEMON_OPTIONS listed above only for smtp.

[root@linuxtruth.org ~]# nano /etc/mail/sendmail.mc

DAEMON_OPTIONS( `Port=smtps, Name=TLSMTA, M=s')