Apr 12, 2016 · When the sender email address or domain is examined for a match: email addresses and domain names in the list are compared to the sender address in the message envelope (MAIL FROM:) and message header (From:) IP addresses are compared to the IP address of the SMTP client delivering the email, also known as the last hop address Don't just flat-out filter anything where the envelope sender (which is what the "return-path" is really called) doesn't match the From: header. Them differing is perfectly legal and used a lot by legitimate services to send mail in your stead without tripping SPF-like protections (which act on the envelope sender address). Oct 16, 2013 · From Biztalk, if you want to send a message to a WCF service, we have to instruct the WCF service application/target system to know which method to invoke or serialize this message/request to. In BizTalk, this instruction (SOAP Action) is set by assigning a value to WCF.Action context property. One more more envelope rcpt to commands in the background that are not in the Header. The envelope is what determines where an email is sent. The header To: From: Subject: Date: are all optional data. This is the information that you see in your mail program. The data in the header does not need to match the data in the envelope. Email Header Fundamentals . If you have a Comcast email, you may receive spam, scams, and other dangerous emails. If you will conduct a Comcast user lookup to find out more about the sender, then you have to understand what an email header is. The email header provides identifying information that is attached to every single email. P1 and P2 Headers in SMTP Posted on February 13, 2006 September 30, 2013 Brian Reid Posted in 2007 , 2010 , 2013 , exchange P1 = the value on the MAIL FROM command of the SMTP connection (the message envelope) as defined in RFC 82 1 .