Any of the following envelope fields ...



... any of the keyword(s):

Compares fields against the envelope

The envelop is equivalent to the mail delivery protocol. So it does not test against a real header. Instead uses trace information from the mail delivery protocol for specific values.

A "to" tests the SMTP sender field "RCPT TO" a "from" the recipient "MAIL FROM".

It is the most reliant way to test from which address a message was send to or received.

Compares headers against constant strings.

You typically use this test with headers containing subject line or a spam score.

Do not use this test, if the header should be matched against a mail addresses. The result will be unrealiable, as this test is not aware of display names. Use the address test instead.