Learn how to set up Sendmail with ClamAV and MILTER Support. Our Sendmail Support team is here to help you with your questions and concerns.

How to Set Up Sendmail with ClamAV and MILTER Support

Did you know that Sendmail integrates seamlessly with MILTER and ClamAV to enhance email security and filtering capabilities?

Our Experts have compiled this step-by-step guide to help you start configuring this setup.

 

Step 1: Check for MILTER Support

Sendmail requires MILTER support to function with filters. To verify if MILTER is enabled, run:

$ sendmail -d0 < /dev/null | grep MILTER

If MILTER appears in the output, proceed to the next step. For systems like RedHat Linux, ensure the `sendmail` and `sendmail-devel` packages are installed:

# yum install sendmail sendmail-devel

If using Sendmail 8.12, add the following entries to `site.config.m4` and rebuild:


APPENDDEF(`confENVDEF', `-DMILTER')
dnl APPENDDEF(`conf_libmilter_ENVDEF', `-D_FFR_MILTER_ROOT_UNSAFE')


To rebuild Sendmail:

$ sh Build -c -f /etc/mail/site.config.m4

Then, ensure the `libmilter` library is installed:

$ locate libmilter | grep /usr/local

If not, install it from the Sendmail source directory:


$ cd libmilter
$ sh Build install


Step 2: Configure ClamAV with MILTER Support

Now, we have to make sure ClamAV is configured with MILTER support. From the ClamAV source directory:

$ ./configure --enable-milter
$ make && make install


Then, update `clamd.conf` with critical options:


LocalSocket /var/run/clamav.sock
LogSyslog
FixStaleSocket
StreamSaveToDisk
StreamMaxLength 10M
User clamav
ScanMail
ScanArchive
ArchiveMaxFileSize 10M


Next, start the ClamAV daemon:

$ sudo /usr/local/sbin/clamd

Step 3: Launch ClamAV-MILTER

Now, start the ClamAV-MILTER service with the appropriate options:


$ sudo /usr/local/sbin/clamav-milter --max-children=2 -olb \
local:/var/run/clamav-milter.sock


For testing, use `–max-children=2`. Increase this value for production use.

Then, create a quarantine directory:


# mkdir /var/mail/quarantine/
# chown clamav:clamav /var/mail/quarantine/
# chmod 600 /var/mail/quarantine/


Step 4: Configure Sendmail for ClamAV-MILTER

Next, update the `sendmail.mc` file to enable virus scanning:


INPUT_MAIL_FILTER(`clamav-milter', `S=local:/var/run/clamav-milter.sock, F=T, T=S:4m;R:4m;E:10m')
define(`confINPUT_MAIL_FILTERS', `clamav-milter')


Then, rebuild the `sendmail.cf` configuration file:


# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
# service sendmail reload


Step 5: Test the Configuration

At this point, send a test email with an EICAR test string:

# echo 'X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*' | sendmail -v abc@domain.com

Also, verify the message is quarantined or appropriately flagged by ClamAV.

Additional Notes

• Use `T=S:4m;R:4m` to define timeouts for sending and receiving to/from the filter.
• Also, update ClamAV logs with `LogFile /var/log/clam/clamd.log`.
• Then, increase `–max-children` and other parameters for production systems.

This configuration ensures the Sendmail setup integrates effectively with ClamAV and MILTER, providing robust email filtering and security.

[Need assistance with a different issue? Our team is available 24/7.]

Conclusion

In brief, our Support Experts demonstrated how to set up Sendmail with ClamAV and MILTER Support.