Maximum internet email Message-ID length

Question

I\'m looking for the maximum character length allowed for an internet Message-ID field for validation purposes within an application. I\'ve reviewed sources such as RFC-282

Answer 1

Actually there's no limit

RFC2822 defines these productions:

message-id      =       "Message-ID:" msg-id CRLF

msg-id          =       [CFWS] "<" id-left "@" id-right ">" [CFWS]

id-left         =       dot-atom-text / no-fold-quote / obs-id-left

obs-id-left     =       local-part

local-part      =       dot-atom / quoted-string / obs-local-part

quoted-string   =       [CFWS]
                        DQUOTE *([FWS] qcontent) [FWS] DQUOTE
                        [CFWS]

CFWS            =       *([FWS] comment) (([FWS] comment) / FWS)

FWS             =       ([*WSP CRLF] 1*WSP) /   ; Folding white space

So id-left can be local-part which can be quoted-string (and thus have multiple FWS) so you can fold it as many times as needed to fit any arbitrary length of payload and still comply with the restrictions given by the RFC.