cPanel have created a problem with a recent modification to how webmail, squirrelmail in particular, works on the latest versions of cPanel. In the past, webmail sent using the sendmail binary (exim) and worked without issue. In an attempt to identify outgoing email with the correct cPanel account, squirrelmail is now configured by cPanel to connect directly to the local port 25 under the UID of the account sending email.This causes problems with the cPanel configuration of the security SMTP Tweak option in WHM Server Security which cannot allow through such email without making that option less secure. Enabling it to do so would effectively open up the security tweak in the firewall for any script under a user account to send email out on localhost port 25. There is a workaround option by allowing localhost connections to the SMTP port which will allow squirrelmail to work, but does still reduce the security option level.The SMTP_BLOCK option in csf performs the same iptables configuration as the SMTP Tweak does through WHM and is also affected by this change by cPanel.There are 3 options to workaround this anomaly until cPanel come up with a solution:1. Enable the SMTP_ALLOWLOCAL (“Allow connections to localhost on port 25” option in WHM SMTP Tweak if you don’t use csf) which should allow port 25 connections from localhost (127.0.0.1)2. Disable the SMTP_BLOCK (or WHM SMTP Tweak option if you don’t use csf) option. In doing so, you leave yourself open to exploited scripts sending out spam while bypassing exim3. Use the following workaround mentioned on the cPanel forums:http://forums.cpanel.net/showthread.php?t=71073There is a cPanel bugzilla entry open for this issue:http://bugzilla.cpanel.net/show_bug.cgi?id=5917
