At a glance, the From and Sender header appears identical in an email. However, there is a subtle difference that can play an essential role in some instances. This article explores their differences and discusses the instances when they should differ.
According to the RFC, the From header specifies the author's name and address. On the other hand, the Sender specifies the agent's mailbox responsible for the actual transmission. A sender header is not required, and therefore, is often missing. This is because in most cases they are identical and there is no need for it.
Consider the following scenario as an example:
email@example.com), wants to forward incoming emails to her
From: "John Doe" <firstname.lastname@example.org> To: "Jane Doe" <email@example.com> Subject: Meeting agenda
@gmail.com) because your email server is not authorized to originate an email from
From: "John Doe" <firstname.lastname@example.org> Sender: email@example.com To: "Jane Doe" <firstname.lastname@example.org> Subject: Meeting agenda
C --> HELO mail.yourcompany.com S <-- 250 OK C --> MAIL FROM: <email@example.com> S <-- 250 OK C --> RCPT TO: <firstname.lastname@example.org> S <-- 250 OK C --> DATA S <-- 354 OKA modified value in the
Senderheader will modify the
MAIL FROMvalue in the SMTP envelope. This will cause the receiving server to perform an SPF lookup against
hotmail.com, solving the forgery problem.
Xeams automatically adds the Sender header into any incoming email when expanding a distribution list. A distribution list in Xeams can either be expanded to a single address, similar to the Jane Doe's example above or to multiple recipients. Consider the following scenario as an example:
email@example.com, firstname.lastname@example.org, email@example.com
firstname.lastname@example.org. This message needs to be forwarded to
somewhere.comin a way that it should not be considered a forgery. Therefore, Xeams will add automatically add a Sender header to fix the problem, which will also modify the
MAIL FROMin the envelope.