With the introduction of our own spam protection system , we now have more options to improve the handling of our outgoing mail traffic. It allowed us to become one of the few hosting companies to implement Sender Rewrite Scheme (or Mail SRS) and thus significantly improve email forwarding sending rates for our customers. Here are the details of how this new functionality works and how it benefits our users.
Why are forwarded emails harder to deliver?
Typically, when there is an incoming email, the receiving server tries to identify whether the sending server is legitimate and whether the email should be accepted. The purpose of this verification is to prevent malicious senders from reaching your inbox (for example, a fraudulent email pretending to come from your bank's domain name).
Domain names used for sending legitimate mail must have a Sender Policy Framework (SPF) record, which defines the IP addresses or hosts that are allowed (or not allowed) to send messages on behalf of this domain.
In the email forwarding scenario, we have a sender who is sending an email to a destination address and after that, the destination address forwards the email to its final recipient. This means that the final recipient is receiving an email coming from a “middleman” server, which might not be allowed to send messages on behalf of the sending domain, according to its SPF record.
This, based on the policies of the receiving servers, may result in emails being rejected or sent to your Spam folder due to a failure in SPF (Sender Policy Framework).
How does SRS make email forwarding more reliable?
Sender Rewrite Scheme (or Mail SRS) is a mechanism that provides a solution in email forwarding cases to avoid SPF failures. In this way, legitimate forwarded emails can be successfully accepted from the receiving mail server.
SRS works by rewriting some of the metadata in email messages after they pass the mediating server, “instructing” the destination mail server to check the SPF against the forwarding server, not the original sender’s domain. That way, the SPF check would pass because the forwarding server’s IP would match the sender’s address. Here’s a real-life example of how this works:
Imagine that a servic
If there is no SRS, Gmail will see an email sent frrbank.com but origi hong kong whatsapp number data nating from a SiteGround IP. Since these two do not match, the SPF check will not pass and Gmail will probably deliver the email to the Spam folder.
If the SRS is configured correctly, the “from” address will be changed to webnt email from your bank in your personal mailbox as well.
This makes SRS an important part of every mail server configuration to maintain the efficiency and reliability of email forwarding services, ensuring that important communications are not mistakenly marked as spam or rejected due to SPF checks.
Results of SRS implementation
We are already seeing a very positive impact on the deliverability of forwarded emails after SRS became available on our servers. Our data shows 0% SPF failures for all forwarded emails passing through our servers, which demonstrates incredible stability and reliability of our mail service and improves the reputation of our mail system addresses. Needless to say, all of this also directly benefits the mail reputation of customer domains hosted on our servers.
