Revert "Merge pull request #15951 from mcav/smtp-mail-from"

This reverts commit 7429e25940e2c69582cf850bf99652f37117a3d5, reversing
changes made to 369d6998876b78305a727ecfc4c65ed23792cc10.
Bug 948580 - [B2G][Email] Send "MAIL FROM" in SMTP probe to validate e-mail address. r=asuth