Ages ago, Sendmail added an errant "!", causing overruns -- I think that's in part why the prior Postfix value == 990? to accommodate 'broken' Sendmail?
Time's passed, clearly the Postfix default has been raised to ==998, but ... has Sendmail actually been fixed to be 998-char compliant? And, in wide enough real-world deployment to be an acceptable risk?
Or is the real-world recommendation still to dumb-down to == 990?
The maximum total length of a text line including the <CRLF> is 1000
octets (not counting the leading dot duplicated for transparency).
This number may be increased by the use of SMTP Service Extensions.
Postfix doc says:
smtp_line_length_limit (default: 998)
The maximal length of message header and body lines that Postfix will
send via SMTP. This limit does not include the <CR><LF> at the end of
Which is consistent with RFC 5321.
> Ages ago, Sendmail added an errant "!", causing overruns -- I think
> that's in part why the prior Postfix value == 990? to accommodate
> 'broken' Sendmail?
Postfix HISTORY says:
Cleanup: more graceful handling of long physical message
header or body lines upon output by the SMTP client. The
SMTP client output line length is controlled by a new
parameter smtp_line_length_limit (default: 990; specify 0
to disable the limit). Long lines are folded by inserting
<CR> <LF> <SPACE>, to avoid breaking MIME encapsulation.
Based on code by Victor Duchovni, Morgan Stanley. File:
Cleanup: for consistency with the SMTP standard, the
smtp_line_length_limit default value was increased from 990
characters to 998 (i.e. 1000 characters including <CR><LF>).
File: global/mail_params.h, proto/postconf.proto.