Sendmail+Cyrus IMAP "Data format error" and bounces

[Deborah Pickett]

Hi Andrea,

On 2020-03-17 20:57, Andrea Venturoli wrote:
> From time to time, I receive some message that are refused and bounce.
> Do to possible blacklisting, I *really* want to avoid bounces.
>
> Here's a sample log:
> sm-mta[97841]: 00DI1r4x097841: from=<in... at services.xxx.com>, size=37059,
> class=0, nrcpts=1,
> msgid=<PATT3L844_19452433_q5ZeSIsrRLtOGReCXrQXgg==.8A... at xxxxxxxxxxx.xxxxxxxx.net>, 
>
> proto=UTF8SMTPS, daemon=MTA, relay=xxxxxxxxxxx.xxxxxxxx.net 
> [37.148.183.222]
> sm-mta[97960]: AUTH=client, relay=localhost, mech=, bits=0
> sm-mta[97960]: 00DI1r4x097841: to=xxxxxxxxxx, delay=00:00:11,
> xdelay=00:00:00, mailer=cyrusv2, pri=67551, relay=localhost, dsn=5.6.7,
> stat=Data format error
> sm-mta[97960]: 00DI1r4x097841: 00DI264w097960: DSN: Data format error
> sm-mta[97960]: 00DI264w097960: to=<in... at services.xxx.com>,
> delay=00:00:04, xdelay=00:00:04, mailer=esmtp, pri=30000,
> relay=mx1.slgnt.eu., dsn=5.1.2, stat=Host unknown (Name server:
> xxx.xxxxx.xx.: no data known) 

I don't use sendmail but I do use the same version of Cyrus that you do.

The status 5.6.7 seems to be related to encodings.  It's defined in RFC 
6531, SMTP Extension for Internationalized Email:

When the SMTPUTF8-aware SMTP
server supports enhanced mail system status codes [RFC3463], reply-
code "X.6.7" [RFC5248] (see Section 4) is used, meaning "Non-ASCII
addresses not permitted for that sender/recipient".
[source: https://tools.ietf.org/html/rfc6531#section-3.5]

Do all of the failures have proto=UTF8SMTP(S) in them, or just this example?

For posterity, here is your post on the sendmail group, which I have 
read: https://groups.google.com/forum/#!topic/comp.mail.sendmail/5F2UZgAYrnI
I agree with them that your anonymization of the log with xxx may have 
masked important information.  There may be temporary DNS failures going 
on but it's impossible to tell.

-- 
Deborah Pickett
System Administrator
Polyfoam Australia Pty Ltd