All You Need to Know About E-mail Authentication

SIDF, created by Microsoft, is similar to SPF. SPF verifies the visible “from” line of the e-mail, while SIDF authenticates either the “from” line or the invisible “from” line of the e-mail header. Using the U.S. Postal Service as an analogy, SIDF is akin to verifying the authenticity of both the outer envelope and the letterhead on the document inside the envelope.