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Saty_Attota_201's avatar
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Jul 02, 2018

SMTP mail - getting error 550 5.7.1 Unable to relay for

I did set up mailhub. Could see entry in /etc/ssmtp/ssmtp.conf as expected.


Created SMTP configuration from System -> Device -> SMTP


Later I issued the following commands:


modify /sys outbound-smtp mailhub save /sys config


I tested with following mail command: echo "Test message" | mail -vs "Test message"


But I am getting error. I could telnet to mail server. Here is the log


echo "Test message" | mail -vs "Test message" [<-] 220 Microsoft ESMTP MAIL Service, Version: 8.5.9600.16384 ready at Mon, 2 Jul 2018 11:34:45 -0700 [->] HELO [<-] 250 Hello [] [->] MAIL FROM: [<-] 250 2.1.0 OK [->] RCPT TO: [<-] 550 5.7.1 Unable to relay for send-mail: RCPT TO: (550 5.7.1 Unable to relay for


Can someone suggest how to resolve this problem.


Thanks in advance


3 Replies

  • Here is additional comment.


    telnet host 25 is successful with return code 220


    helo testing returned succeful code 250


  • Forgot to mention that I added f5 ip address in relay list too. No problem with firewalls


  • You should be able to telnet from the BIGP-IP to Exchange and send an email. If that cannot happen, Exchange still needs further configuration. In this case, you're using BIG-IP like any telnet client.


    1. Verify the IP you specified to relay IS the actual IP being used. If you setup automap versus SNAT pool. BIG-IP can have many sending IP addresses so SMTP/Transport Agent logs will verify (or tcpdump/wireshark the Exchange Transport/CAS box).
    2. Is requires authentication enabled for the receive connector? 550 5.71 can fail due to the receive connection auth settings.
    3. Is the setup as a receiving domain for this? The failure happened immediately after RCPT instead of completing the mail setup .

    You should be able to complete a basic SMTP handshake in any telnet client to validate this works. If that fails, you'll need to investigate the incoming receive connector, transport agent, and other Exchange related configs prior. Best step is to simplify the config to basic send/receive before introducing new configs and proxies.


    If you want, obfusicate and send along transport logs of the session.