we are running a mail server and always the same error in the logs (for a specific recipient):
Aug 23 05:39:17 Mailer postfix/smtp[13561]: warning: DANE
TLSA lookup problem: Host or domain name not found. Name
service error for name=_25._tcp.dhmx02.web.de type=TLSA:
Host not found, try again
Aug 23 05:39:17 Mailer postfix/smtp[13561]: warning: TLS
policy lookup for xyz.com/dhmx02.web.de: TLSA lookup
error for dhmx02.web.de:25
Aug 23 05:39:17 Mailer postfix/smtp[13561]: 9BEA23EC68:
to=<[email protected]>, relay=none, delay=4509,
delays=4236/0.05/272/0, dsn=4.7.5, status=deferred
(TLSA lookup error for dhmx02.web.de:25)
The emails come back with the following information:
This is the mail system at host mx00.unser-mail-server.com.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<[email protected]>: TLSA lookup error for dhmx02.web.de:25
Reporting-MTA: dns; mx00.unser-mail-server.com
X-Postfix-Queue-ID: 9BEA23EC68
X-Postfix-Sender: rfc822; [email protected]
Arrival-Date: Mon, 23 Aug 2021 04:24:08 +0200 (CEST)
Final-Recipient: rfc822; [email protected]
Original-Recipient: rfc822;[email protected]
Action: failed
Status: 4.7.5
Diagnostic-Code: X-Postfix; TLSA lookup error for dhmx02.web.de:25
The following software is used on the server (Debian 10):
root|mailer|/etc/rspamd|# dpkg --list | egrep -i -- "(unbound|postfix|rspam|dovecot)"
ii dovecot-core 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - core files
ii dovecot-imapd 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - IMAP daemon
ii dovecot-lmtpd 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - LMTP server
ii dovecot-managesieved 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - ManageSieve server
ii dovecot-mysql 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - MySQL support
ii dovecot-sieve 1:2.3.4.1-5+deb10u5 amd64 secure POP3/IMAP server - Sieve filters support
ii libunbound8:amd64 1.9.0-2+deb10u2 amd64 library implementing DNS resolution and validation
ii postfix 3.4.14-0+deb10u1 amd64 High-performance mail transport agent
ii postfix-mysql 3.4.14-0+deb10u1 amd64 MySQL map support for Postfix
ii rspamd 2.5-1~bpo10+1 amd64 Rapid spam filtering system
ii unbound 1.9.0-2+deb10u2 amd64 validating, recursive, caching DNS resolver
ii unbound-anchor 1.9.0-2+deb10u2 amd64 utility to securely fetch the root DNS trust anchor
Unbound is used as resolver on the server, can this be the reason?
How can I fix the TLSA lookup error for dhmx02.web.de:25? IT seems that it's realated to the receivers server, but he claims that he can't receive emails only from our mail server.
Does anyone have a clue how to solve the problem?
