Just like physical letters, an email message has two sets of addresses: the envelope address and the message header address. The envelope address, like the address on the outside of an envelope, is used by the MTA to route and deliver the email message; the message header address, which is part of the message header, is similar to the address attached to a salutation at the start of a physical letter.
The Sender Filter Settings screen enables you to choose the type of sender addresses Hosted Email Security uses to match the approved or blocked sender list.
The following options are available:
By default, this option is selected and cannot be modified.
Message header addresses
If you select this option, Hosted Email Security uses both addresses for matching.
However, note that message header addresses in the approved sender list cannot bypass IP reputation-based filtering.
Unless specified otherwise, Hosted Email Security considers the envelope address as the common sender address.