Wondering how to disable ipv6 in sendmail? Our in-house experts are here to help you out with this article. Our sendmail support is here to offer a lending hand with your queries and issues.

Disable ipv6 in sendmail

Today, let us see the steps followed by our support techs to disable ipv6.

1.Firstly, edit /etc/mail/sendmail.mc

2.Then, look for

DAEMON_OPTIONS(`Port=smtp,Addr=xxx.xxx.xxx.xxx, Name=MTA')dnl

Below the above line add this;

CLIENT_OPTIONS(`Family=inet6,Addr=::ffff:xxx.xxx.xxx.xxx')dnl

3.Save the file, make the db files and restart Sendmail.

4.Now, Sendmail will use IPv4 for it’s CLIENT operations.

In your sendmail.mc add:

CLIENT_OPTIONS(`Family=inet')dnl

5.Then, rebuild sendmail.cf and restart sendmail. In Debian you do this by running sendmailconfig.

In CentOS you run /etc/mail/make follow by service sendmail restart. Other systems have other ways to do this.

CLIENT_OPTIONS(`Family=inet6,Addr=::ffff:0.0.0.0')dnl

which forces sendmail to use your IPv6 when it wants to use inet6

add the above into /etc/mail/sendmail.mc below the existing CLIENT_OPTIONS line

How To Disable IPv6 w/ Sendmail on FreeBSD

Edit /etc/make.conf to ensure that IPv6 is turned off for Sendmail compiles. Add this line to the file:

SENDMAIL_CFLAGS= -UNETINET6

Rebuild Sendmail :

# cd /usr/src/lib/libsmutil
# make cleandir && make obj && make
# cd /usr/src/lib/libsm
# make cleandir && make obj && make
# cd /usr/src/usr.sbin/sendmail
# make cleandir && make obj && make && make install

Then, go into your Sendmail config directory (/etc/mail), and if you haven’t so before, run make all to build your machine-specific Sendmail config files.

Then, edit hostname.mc and locate the line that reads DAEMON_OPTIONS(`Name=IPv6, Family=inet6, Modifiers=O’) and comment it out by adding a dnl in front of it:

dnl DAEMON_OPTIONS(`Name=IPv6, Family=inet6, Modifiers=O’)

Compile the Sendmail config and restart Sendmail:

make install
make restart

And, now you’re done! Look at /var/log/maillog to ensure that mail is no longer being delivered via IPv6.

[Looking for a solution to another query? We’re happy to help.]

Conclusion

In this article, we provide a quick and simple solution from our Support team to disable ipv6 in sendmail