Email forwarding problem/Bibliography

RFCs
RFC-4405 (2006), "SMTP Service Extension for Indicating the Responsible Submitter of an E-Mail Message", E. Allman, H. Katz, http://tools.ietf.org/html/rfc4405. IETF Experiment.

RFC-4406 (2006), "Sender ID: Authenticating E-Mail", J. Lyon, M. Wong, http://tools.ietf.org/html/rfc4406. IETF Experiment.

RFC-4408 (2006), "Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1", M. Wong, W. Schlitt, http://tools.ietf.org/html/rfc4408. IETF Experiment.

RFC-4871 (2007), "DomainKeys Identified Mail (DKIM) Signatures", E. Allman et.al., http://tools.ietf.org/html/rfc4871. IETF Proposed Standard.

RFC-5451 (2009), "Message Header Field for Indicating Message Authentication Status", M. Kucherawy, http://tools.ietf.org/html/rfc5451. IETF Proposed Standard. A new email header field with results of message authentication.