Mail forwarding to external addresses: be careful

cPanel mail forwarders allow you to forward mail to other mail accounts on the same web hosting server or to external addresses. Be careful when forwarding to external addresses, as it could result in your server being blacklisted and thus unable to send mail to some places.

When you create a forwarder such as for you@yourdomain.com to forward to an external address, such as joe@Hotmail.com, all mail addressed to you@yourdomain.com will go to the external mailbox. That includes legitimate mail and, of course, spam and possibly malware. That’s where the problem begins.

Any spam sent to your mail forwarder address is immediately forwarded to the external address, where the receiving server may conclude that your hosting server sent the spam (or at least relayed it, which it did) and therefore blacklist the server. Once the server is on a blacklist, any mail sent from your server will be rejected by many ISPs and mail providers.

If the external address is at AOL, then the AOL user can compound the problem by hitting the “This is spam” button. AOL sees your web hosting server as the last relay of the spam, and suddenly you are the bad guy. AOL has blacklisted web hosting servers many times because of this.

Mail forwarding to external addresses can be useful. However, you must be careful and stay informed because some mail operators, such as AOL, are particularly likely to block servers such as these for forwarding mail.

You should never forward to AOL. You may Google for other articles to verify my opinion, as this is a widespread problem. AOL blacklists often for forwarded mail, so you should advise your hosting clients and users never to forward to AOL. Forwarding to Hotmail and RoadRunner has also been problematic at times, because they also have a history of often blacklisting for forwarding. We could likely add other ISPs and mail providers to that list, who often block shared servers due to mail forwarding.

I recently confronted this issue again for two client companies. Both use cPanel forwarders to ISP mail accounts. Due to blacklisting of my reseller web hosting server’s mail server IP, the ISP blocked mail from our web hosting server. Result: those users were unable to receive any mail from their mail forwarders, so they were receiving no mail at all since the forwarders are their primary addresses.

Never forward to AOL, be cautious when forwarding to Hotmail or RoadRunner, and be vigilant when forwarding anywhere else. This problem will likely grow more common due to the growing spam volume that ISPs combat.