smtputf8

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smtputf8

Drexl Spivey
Hello,

From what I have read, smtputf8 is enabled by default to 'yes' in
postfix version greater than 3.

I also read through the Postfix documentation, that just because it's
supported by Postfix, there are many subsystems (like Dovecot) that do
not.

I wouldn't have even given it much though, until today, some emails
(from one sender) were getting bounced back. If I read the logs
correctly, the emails were excepted by postfix, forwarded to Dovecot,
where they were rejected. The log looks a little bit like this:

May  5 19:47:18 mail postfix/qmgr[1478]: BFD821980453: from=<karten@exa
mple.de>, size=44302, nrcpt=1 (queue
active)                                                                
                                                                       
                                                   │
│May  5 19:47:18 mail postfix/smtp[1384]: 6CE401980455: to=<musica@musi
c.com>, relay=127.0.0.1[127.0.0.1]:10026, delay=0.75,
delays=0.25/0.11/0.08/0.31, dsn=2.0.0, status=sent (250 2.0.0 Ok:
queued as
BFD821980453)                                                          
                                     │
│May  5 19:47:18 mail clamsmtpd: 100197: from=[hidden email], to=mus
[hidden email],
status=CLEAN                                                           
                                                                       
                                                                    │
│May  5 19:47:18 mail postfix/smtpd[1388]: disconnect from
localhost.music.com[127.0.0.1] ehlo=1 xforward=1 mail=1 rcpt=1 data=1
quit=1
commands=6                                                             
                                                                       
                               │
│May  5 19:47:18 mail postfix/qmgr[1478]: 6CE401980455:
removed                                                                
                                                                       
                                                                       
                                              │
│May  5 19:47:18 mail dovecot: lmtp(1395): Debug: SSL: elliptic curve
secp384r1 will be used for ECDH and ECDHE key
exchanges                                                              
                                                                       
                                                         │
│May  5 19:47:18 mail dovecot: lmtp(1395): Debug: none: root=, index=,
indexpvt=, control=, inbox=,
alt=                                                                   
                                                                       
                                                                       
  │
│May  5 19:47:18 mail dovecot: lmtp(1395): Connect from
local                                                                  
                                                                       
                                                                       
                                              │
│May  5 19:47:18 mail postfix/lmtp[1394]: BFD821980453: to=<musica@musi
c.com>, relay=mail.music.com[private/dovecot-lmtp], delay=0.47,
delays=0.3/0.03/0.14/0, dsn=5.6.7, status=bounced (SMTPUTF8 is
required, but was not offered by host mail.music.com[private/dovecot-
lmtp])                        │
│May  5 19:47:18 mail dovecot: lmtp(1395): Disconnect from local:
Successful
quit                                                                   
                                                                       
                                                                       
                         │
│May  5 19:47:18 mail postfix/cleanup[1356]: 635D91980455: message-id=<
[hidden email]>                            
                                                                       
                                                                       
                         │
│May  5 19:47:18 mail postfix/bounce[1397]: BFD821980453: sender non-
delivery notification: 635D91980455

I have enabled in the postfix main.cf:
smtputf8_enable=no


It appears like this is exactly the case: Postfix is accepting the
mail, but it is getting denied by Dovecot?? Is my understanding
correct?

Which leads to my next question, why is smtputf8 even enabled at all,
by default? What are the advantages if it only will prevent some email
from being received? Surely, there must be some advantages? I am not
being facetious, I really don't know.

Thanks for reading!



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Re: smtputf8

Wietse Venema
Esteban L:
> Which leads to my next question, why is smtputf8 even enabled at all,
> by default?

Because Dovecot is not the only mail delivery system.

> What are the advantages if it only will prevent some email from
> being received? Surely, there must be some advantages? I am not
> being facetious, I really don't know.

Because there is other software that does support SMTPUTF8.

Consider the alternative: everything turns off SMTPUTF8 by default
until everything else supports it.

You can turn off Postfix SMTPUTF8 support, and then you will never
know why some messages did not arrive. Unlike 8BITMIME, SMTPUTF8
does not provide automatic conversion.

        Wietse