Disallowed Off-Site Email Forwarders
In today's heavy spam climate, when an ISP receives any email item, they usually test it against a range of criteria to determine its level of spam probability. If the item is found to be spammy, the email may be passed for special handling to be marked as spam, stored in a spam folder, or rejected.
Another anti-spam tool which many ISP's employ is the recording and flagging of SMTP servers found to be originating unusually high levels of spammy items. When an email is transported via the SMTP system to its final destination, it can collect header information which is useful in determining both the origin and travelled path of the email item. Generally then, when an email item is found to be spammy, any penalty flag which is recorded is applied against the originating SMTP server which first allowed the email item to enter the email system.
However, ISP's are free to handle email entering their network in any way that suits them, and a few ISP's tend to flag the last server to touch the email instead of, or as well as, the actual originating server which raised the item. It is this handling that can cause issues when clients configure offsite email forwarders on their servers pointing to ISP's in this particular group.
If you create an offsite forwarder to send incoming email to an ISP who flags based on the last touching server, your own server can be flagged for sending on the incoming email which you actually want to receive and deal with at your final target mailbox. You then run the very real risk of missing email which your ISP has rejected, and the problem is compounded by affecting all other clients on your same physical server.
Accordingly, GCom Internet strongly recommends that clients do not create an offsite forwarder unless there is a very good reason why the creation of a full email account will not satisfy their specific email handling requirements.
At some future date we may need to disallow all offsite forwarders, but at this stage we are looking at each offsite forwarder configuration on a case by case basis.
Currently we will not permit offsite forwarders to remain in place if the final target email address includes any of the following set of domains...
Please always configure full email accounts for the above target domains instead of using forwarders for your email handling.