smtp_line_length_limit vs Sendmail?

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smtp_line_length_limit vs Sendmail?

PGNet Dev
Current default for

 http://www.postfix.org/postconf.5.html#smtp_line_length_limit

is == 998, per smtp std.

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?




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Re: smtp_line_length_limit vs Sendmail?

Wietse Venema
PGNet Dev:
> Current default for
>
> ?http://www.postfix.org/postconf.5.html#smtp_line_length_limit
>
> is == 998, per smtp std.

RFC 5321 says:

4.5.3.1.6.  Text Line

   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
       each line.

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:

20020324

        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:
        smtp/smtp_proto.c.

20111011

        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.

I don't see any mention of Sendmail in that text.

        Wietse
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Re: smtp_line_length_limit vs Sendmail?

PGNet Dev
> I don't see any mention of Sendmail in that text.

As I said, 'ages ago'.  Per a conversation,

  https://mailing.postfix.users.narkive.com/nhbtm7Fg/smtp-line-length-limit-998

It apparently was an issue; I'm asking if it still is.
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Re: smtp_line_length_limit vs Sendmail?

Wietse Venema
PGNet Dev:
> > I don't see any mention of Sendmail in that text.
>
> As I said, 'ages ago'.  Per a conversation,
>
>   https://mailing.postfix.users.narkive.com/nhbtm7Fg/smtp-line-length-limit-998
>
> It apparently was an issue; I'm asking if it still is.

The limit was still 990 in Sendmail 8.15.

        Wietse
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Re: smtp_line_length_limit vs Sendmail?

PGNet Dev
> The limit was still 990 in Sendmail 8.15.

To deal with that in production, is setting value in Postfix to == 990 sufficient? recommended?

Does a setting of == 990 (continue to) break any particular service/functionality?

The Sendmail 'Usenet'/Google Group is a bit of a sewer; cc'ing Claus to see if there's any newer comment/clarity as to why Sendmail's still not standards-compliant in this.

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Re: smtp_line_length_limit vs Sendmail?

Wietse Venema
In reply to this post by Wietse Venema
Wietse Venema:

> PGNet Dev:
> > > I don't see any mention of Sendmail in that text.
> >
> > As I said, 'ages ago'.  Per a conversation,
> >
> >   https://mailing.postfix.users.narkive.com/nhbtm7Fg/smtp-line-length-limit-998
> >
> > It apparently was an issue; I'm asking if it still is.
>
> The limit was still 990 in Sendmail 8.15.

And in the more recent sendmail.8.16.0.41.

  Wietse
 
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Re: smtp_line_length_limit vs Sendmail?

Wietse Venema
In reply to this post by PGNet Dev
PGNet Dev:
> > The limit was still 990 in Sendmail 8.15.
>
> To deal with that in production, is setting value in Postfix to
> == 990 sufficient? recommended?

No idea. One could equally-well argue for setting it to zero.

        Wietse
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Re: smtp_line_length_limit vs Sendmail?

Claus Assmann-22
In reply to this post by PGNet Dev
On Mon, Dec 16, 2019, PGNet Dev wrote:

> The Sendmail 'Usenet'/Google Group is a bit of a sewer; cc'ing Claus to see if there's any newer comment/clarity as to why Sendmail's still not standards-compliant in this.

Please do NOT use my private e-mail address on a public mailing list
-- now you just "burned" it!

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Re: smtp_line_length_limit vs Sendmail?

PGNet Dev
In reply to this post by Wietse Venema
> No idea. One could equally-well argue for setting it to zero.

Noted.

It was changed here long-ago, guessing for a reason, but I've no current metrics to convince me, or not, that there's a problem (anymore).

My inclination is to stick with Postfix's 'new(er)' default/standard == 998, for no other reason than it IS the default/standard.

And simply allow the non-compliant "rest" cause whatever problems they will ...