/etc/dovecot/conf.d/10-master.conf

service auth {
…
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }
…
}

/etc/dovecot/conf.d/10-auth.conf

…
# Outlook and Windows Mail works only with LOGIN mechanism, not the standard PLAIN:
auth_mechanisms = plain login
…

systemctl restart dovecot.service

Testen:

ls -l /var/spool/postfix/private/auth
lsof /var/spool/postfix/private/auth

postconf -e 'smtpd_sasl_type = dovecot'
postconf -e 'smtpd_sasl_path = private/auth'
postconf -e 'smtpd_sasl_auth_enable = yes'

swaks --from me@example.com --to you@example.com -s localhost -a -au nutzer14 -ap test

Encodiertes Passwort erzeugen:

perl -MMIME::Base64 -e 'print encode_base64("iw\0iw\0passwort")'

oder:

echo -en "iw\0iw\0passwort" | mimencode

Authentifizierung testen:

netcat -v localhost 25
220 notebook12.linuxhotel.de ESMTP Postfix (Debian/GNU)
EHLO localhost
250-localhost
250-AUTH LOGIN PLAIN
AUTH PLAIN aXcAaXcAdGVzdA==
235 Authentication successful