Hello Benoît Put simply, we do DNS requests for MX or A records for the given sender domain, if either exists this check is passed.
As for the issue at hand: the DNS servers of your customer are (were) not properly reachable from our IP ranges or more specifically we are (were) unable to get the IPs for ns1.aerni.com or ns2.aerni.com. During our investigation this resolution has mostly recovered and we are able to resolve the domain properly, so this issue should now be resolved. This makes it harder though to pinpoint the exact cause here, to us it currently seems though that NS records have been changed and the old DNS servers been turned off before the TTLs of the old NS records had expired, so some intermediate DNS/CNS servers still had cached info that was now no longer working and this made the domain unresolvable to our servers. As a side note: both NS entries now share a single IP and that is even the same IP as the mail server, this is definitely not an optimal setup, an offsite secondary DNS server that didn't need changing might have prevented this from the start. Regards Marcel -----Ursprüngliche Nachricht----- Von: swinog-boun...@lists.swinog.ch [mailto:swinog-boun...@lists.swinog.ch] Im Auftrag von Benoit Panizzon Gesendet: Freitag, 12. Januar 2018 10:31 An: email@example.com Betreff: [swinog] Bluewin Error: Der MX-Eintrag fuer die Domaene aerni.com kann nicht verifiziert werden Hello List Does anyone know, how bluewin does 'verify' an MX? The MX of our customer is prefectly reachable for sender verification but his emails sent 'to' bluewin recipients are getting blocked with: MAIL FROM: <[scrubbed]@aerni.com> Unable to verify MX-Record for domain aerni.com aerni.com mail is handled by 10 mail.aerni.com. mail.aerni.com has address 18.104.22.168 Connected to mail.aerni.com. Escape character is '^]'. 220 mail.aerni.com ESMTP ready. quit 221 mail.aerni.com closing connection Connection closed by foreign host. benoit@krup:~$ telnet mail.aerni.com. smtp Trying 22.214.171.124... Connected to mail.aerni.com. Escape character is '^]'. 220 mail.aerni.com ESMTP ready. ehlo imp.ch 250-mail.aerni.com Hello dhcp-186.imp.ch [126.96.36.199] 250-SIZE 52428800 250-8BITMIME 250-PIPELINING 250-AUTH PLAIN LOGIN 250-STARTTLS 250 HELP mail from:<> 250 OK rcpt to:<[scrubbed]@aerni.com> 250 Accepted rset 250 Reset OK Mit freundlichen Grüssen -Benoît Panizzon- -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________ _______________________________________________ swinog mailing list firstname.lastname@example.org http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog _______________________________________________ swinog mailing list email@example.com http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog