If you use a mailserver wil very low ram (< 500 MB) and a slow CPU then it might be nescessary to disable the spam and antivirus filter functions in ISPConfig 3, as amavisd and clamav might be too heavy for your server hardware. The steps to disable clamav and amavisd are:

Edit postfix main.cf file

nano /etc/postfix/main.cf

and comment out these lines by adding a ”#” in front of them:

main.cf

[...]
# content_filter = amavis:[127.0.0.1]:10024
# receive_override_options = no_address_mappings
[...]

Then restart postfix:

/etc/init.d/postfix restart

Now stop and disable the services. The following commands are for Debian and Ubuntu, the commands for other Linux distributions may vary

/etc/init.d/clamav-daemon stop
/etc/init.d/clamav-freshclam stop
/etc/init.d/amavis stop
 
update-rc.d -f clamav-daemon remove
update-rc.d -f clamav-freshclam remove
update-rc.d -f amavis remove

The normal mail receive and send functions will still work after this modification. But please be aware that disabling amavisd and clamav will disable all antispam & antivirus filtering, so the spamfiltering options that can be configured in the ispconfig interface will have no effect on mail delivery, and no spam and viruses will get filtered.

The changes in postfix main.cf will get overwitten by a ispconfig software update when you select to reconfigure services during upadte, so you should comment out the lines again after you install a ispconfig update.