Sender Rewriting Scheme (SRS) helps improve email deliverability
Gandi provides the SRS (Sender Rewriting Scheme) feature to enable outgoing emails to preserve their authentication even when forwarded. This rewrite of the sender’s address during a transfer enables them to comply with the standards of anti-spoofing filters, and therefore improves the deliverability of outgoing emails.
Spoofing is a type of fraudulent impersonation of the sender’s address: you think you’re receiving a message from a legitimate address, associated with a recognized domain name, but the message actually comes from a completely different IP address that has impersonated the email address.
To prevent this kind of abuse, email services filter incoming emails and require certain forms of authentication. One of these is the Sender Policy Framework (SPF), which indicates which IP addresses are authorized to send mail from a given domain. By configuring the SPF, you can guarantee your recipients that the server from which your message is sent is in fact authorized to use the sender’s address. Your recipient’s email system will then readily accept the message and not block it.
Authentication lost during forwarding
However, this authentication system has one drawback: when an email is forwarded, because the recipient has changed address or is on a mailing list, the new delivery address may consider it to have come from an unauthorized source for that sender (MAIL FROM). In this case, the authentication is invalid and the message is blocked, despite the authentication provided by the sender.
To reach this new recipient, the sender’s address must be rewritten in order to match the IP addresses authorized to use it. The Sender Rewriting Scheme is precisely this: rewriting the sender’s address in a special format to restore its authorization.
Since May 2023, Gandi’s MailBox offer has been enhanced with this functionality, enabling users to experience fewer bounces and greater deliverability of their emails. Email hosting is available in standard (10 GB storage) and premium (50 GB storage) versions, featuring anti-spam filters, a feature for recovering deleted emails, and an unlimited number of aliases.