Increment Connection Ratelimit - ispip.net (local.home) [XX.XX.XX.XX]:61647 because of RBL match
JunkMail rejected - ispip.net (local.home) [XX.XX.XX.XX]:61647 is in an RBL, see http://www.spamhaus.org/query/bl?ip=XX.XX.XX.XX
SMTP connection from ispip.net (local.home) [XX.XX.XX.XX]:61647 I=[YY.YY.YY.YY]:465 closed by DROP in ACL

Do your customers report this error frequently? This happens when your customer’s ISP is blacklisted, leading to your customer’s mail being bounced.

Of course, neither you nor your customer can control which IP your customer’s net connection uses, but inability to send mails through your server affects your customer’s business. Disabling RBL check is not an option as it will make your server susceptible to spam.

Our help desk support team recommends the following two steps to prevent this error without having to compromise cPanel server security.

1. Enforce SMTP authentication

Exim does not check ISP IP’s RBL status if the customer uses SMTP authentication. So, the simple solution to avoid Increment Connection Ratelimit is to enforce SMTP authentication.

cPanel by default, enables SMTP authentication. However, some servers have the “antirelayd” daemon turned on, which enables POP before SMTP, which in turn invalidates SMTP authentication. To enforce SMTP authentication, just go to WHM >> Service Configuration >> Service Manager and disable “Antirelayd” check box. Then restart Exim.

2. Keep RBL list clean

cPanel by default uses only 2 RBLs, viz., bl.spamcop.net, and zen.spamhaus.org. Some servers however, have custom RBL lists to improve spam block effectiveness. Our experience is that, with an increased number of RBLs, we see an increased number of valid mails being blocked, while the spam blocked remain more or less the same in comparison to default lists. To be effective, our team recommends that you do not use more than 2 RBL lists. This reduces the load on the server, and reduces the chance of legitimate customers being blocked.

Increment Connection Ratelimit error most often affects mail users with mobile devices or those who are traveling. With a small change in server policy, you can save your customers a lot of trouble and business downtime, while not compromising server security.

Our help desk support team routinely helps account owners use their service effectively. Here are a few of the common areas we help account owners in:

SEE COMMON ACCOUNT CONFIG ISSUES