SMTP Maximum Body Line Lengths

Handy maximum email message body values to know when debugging email line-folding problems.

Generally if ! or !+ characters are inserted into long email lines, the solution is use shorter lines (insert newlines) or use quoted-printable encoding.

MTA Maximum Octets
RFC821 1000 including CRLF
qmail 990
sendmail standard ESMTP 990
sendmail relay 2040

RFC 821: “The maximum total length of a text line including the <CRLF> is 1000 characters (but not counting the leading dot duplicated for transparency).”

Re: sendmail maximum line length
Dan on Body: Line Length

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