Postfix tries to send emails via some IP that I haven't recognised instead of the MX that it should use -> message bounces. But it the second time it sends to another address of the same domain, it finds the MX normally and delivers the messages. Is there some temporary DNS problems or why does this happen? And what is that mystery IP 5.153.21.206, if the domain's A record is 108.174.149.227? This happens randomly and affects to multiple domains.
Here's a host -command output of the domain: $ host customerdomain.fi customerdomain.fi has address 108.174.149.227 customerdomain.fi mail is handled by 10 mx2.dmail.fi. customerdomain.fi mail is handled by 20 mx1.dmail.fi. $ dig customerdomain.fi ns ... ;; ANSWER SECTION: customerdomain.fi. 901 IN NS dns.site5.com. customerdomain.fi. 901 IN NS dns2.site5.com. Below you can see a log, where I have changed the domains, and emails, but leaved IP's untouched. Mail.log: Mar 12 16:51:06 s1 postfix/qmgr[2918]: 5C0362EBB4: from=<sender+indentification-id-here_customer.email= customerdomain...@our-mail-server-address.fi>, size=24756, nrcpt=1 (queue active) Mar 12 16:51:06 s1 postfix/smtp[13282]: setting up TLS connection to customerdomain.fi[5.153.21.206]:25 Mar 12 16:51:06 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: TLS cipher list "aNULL:-aNULL:ALL:+RC4:@STRENGTH" Mar 12 16:51:07 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: certificate verification depth=2 verify=0 subject=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Certification Authority Mar 12 16:51:07 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: certificate verification depth=2 verify=0 subject=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Certification Authority Mar 12 16:51:07 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: certificate verification depth=1 verify=1 subject=/C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA Limited/CN=COMODO RSA Domain Validation Secure Server CA Mar 12 16:51:07 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: certificate verification depth=0 verify=1 subject=/OU=Domain Control Validated/OU=PositiveSSL Wildcard/CN=*.accountservergroup.com Mar 12 16:51:07 s1 postfix/smtp[13282]: customerdomain.fi[5.153.21.206]:25: subject_CN=*.accountservergroup.com, issuer_CN=COMODO RSA Domain Validation Secure Server CA, fingerprint 04:A3:4B:80:57:10:8D:CA:33:11:03:21:98:87:67:F0, pkey_fingerprint=9A:4B:C2:77:4B:28:F6:90:D9:09:1A:3F:4D:96:62:57 Mar 12 16:51:07 s1 postfix/smtp[13282]: Untrusted TLS connection established to customerdomain.fi[5.153.21.206]:25: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits) Mar 12 16:51:07 s1 postfix/smtp[13282]: 5C0362EBB4: to=< customer.em...@customerdomain.fi>, relay=customerdomain.fi[5.153.21.206]:25, delay=0.81, delays=0.19/0/0.57/0.06, dsn=5.0.0, status=bounced (host customerdomain.fi[5.153.21.206] said: 550-Please turn on SMTP Authentication in your mail client, or login to the 550-IMAP/POP3 server before sending your message. our-mail-server-address.fi 550-[OUR-MAIL-SERVER-IP-HERE]:39982 is not permitted to relay through this server 550 without authentication. (in reply to RCPT TO command)) Mar 12 16:51:07 s1 postfix/pipe[13143]: 358A02EBBA: to=<sender+indentification-id-here_customer.email= customerdomain...@our-mail-server-address.fi>, relay=bounces, delay=0.17, delays=0.01/0/0/0.16, dsn=2.0.0, status=sent (delivered via bounces service) ... Mar 12 16:51:15 s1 postfix/qmgr[2918]: 38F842EBBA: from=<sender+indentification-id-here_another.customer.email= customerdomain...@our-mail-server-address.fi>, size=24754, nrcpt=1 (queue active) Mar 12 16:51:16 s1 postfix/smtp[13079]: 38F842EBBA: to=< another.customer.em...@customerdomain.fi>, relay=mx2.dmail.fi[81.209.127.14]:25, delay=1.2, delays=0.21/0/0.38/0.59, dsn=2.0.0, status=sent (250 2.0.0 t2CCpFO6001374 Message accepted for delivery)
