SMTP Server Authentication
In order to prevent unauthorized people from using your Email server to send their messages, your Virtual
Private Server requires that anyone sending Email through your server has a valid Email address and password for
your server. SMTP-Auth is the new standard for Email server authentication, and provides excellent security with no
management hassles. The way SMTP-Auth works is to incorporate a username/password authentication system into the SMTP server
itself. This effectively eliminates the need to maintain a database of authenticated POP users, which reduces the hassle of
maintenance and the associated security risks.
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Virtual Private Servers that were set up before January 16, 2003 are set up to use the
POP before SMTP anti-relay technique. This is an older
method of authentication that uses a database of authenticated POP users to authorize SMTP access. While it
is an effective anti-relay tool, SMTP-Auth is a better solution, and we recomend that VPS administrators encourage
their customers to begin using SMTP-Auth instead of POP before SMTP.
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The default for new Virtual Private Servers (set up after January 16, 2003) allows users to select either POP before SMTP
or SMTP-Auth authentication as a convenience. The following optional sendmail configuration files are available as
part of the Sendmail M4 Macros (run vinstall sendmail to install
the M4 macros with the alternate configuration files).
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For both POP before SMTP and SMTP-Auth support, replace your default ~/etc/sendmail.cf file with
the one in ~/usr/local/sendmail/cf/cf/default.cf.
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To use SMTP-Auth only, replace your default ~/etc/sendmail.cf file with the
~/usr/local/sendmail/cf/cf/default-auth-only.cf file.
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If you are using procmail, you will need to use the default-procmail-lda.cf or
default-procmail-lda-auth-only.cf files respectively.
Configuring your Email Client Program to use SMTP-Auth
Different Email client programs will require different steps to enable SMTP-Auth. See our
Email Client Configuration pages for instructions on how to
configure your client to use SMTP-Auth. Because of the improved functionality of SMTP-Auth, we stronly recomend
encouraging your users to migrate to the SMTP-Auth method.
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