Email Signature Delimiter

The email signature delimiter is the standardized sequence of characters that marks where the message body ends and the signature begins in plain-text email. The convention is dash-dash-space-newline, written as `-- ` followed by a line break. This sequence was codified in RFC 3676 (Section 4.3) and is recognized by many email clients, mail filters, and quoting tools, which use it to automatically strip or de-emphasize the signature when the recipient replies. The delimiter exists because plain-text email has no other way to distinguish signature from body. In HTML email the delimiter is conventionally omitted because the signature block is visually distinct, but well-formed HTML signatures still include a corresponding plain-text version when the message is sent as multipart/alternative, in which case the delimiter belongs in the plain-text part. Mail clients that respect the convention also use it to abbreviate quoted threads, hiding signatures from the previous-message quote.