RFC 822: Standard for the Format of Arpa Internet Text Messages
Certain basic rules are in uppercase, such as SPACE, TAB, CRLF, DIGIT, ALPHA, etc. Angle brackets are used in rule definitions, and in the rest of this document, whenever their presence will facilitate discerning the use of rule names. 2.2. RULE1 / RULE2: ALTERNATIVES ... This field contains a unique identifier (the local-part address unit ...
DA: 50 PA: 70 MOZ Rank: 10