I need to send mail from sub.domain.com but delivery to one address fails with an error "R=lookuphost defer (-1): host lookup did not complete".

Additional information that might be relevant: My /etc/resolv.conf contains nameservers of a VPS provider (different from domain provider's nameservers). I also checked DNS records of the addressee and found out there was no MX record for it.

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    You should explain what the problem is, not what you think the solution is. – Michael Hampton Mar 31 '14 at 14:42
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    1. Just because there is no MX record, it does not mean that mail cannot be sent there an A record is valid in absence of an MX record. 2. Does this VPS provider's DNS do recursive lookups for you? – NickW Mar 31 '14 at 16:02
  • @NickW I think it does not do recursive lookup. I checked it by "host mysubdomain.domain.com vps_providers_nameserver" and it returned REFUSED; also dig nameserver mysubdomain.domain.com returned "recursion requested but not available" – hiirulainen Mar 31 '14 at 16:43
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    That's not good, you want to configure a DNS server that will do recursive lookups for you, especially if you want to run a mailserver. – NickW Mar 31 '14 at 16:49
  • thank you @NickW I can't upvote your comments but you've been very helpful – hiirulainen Mar 31 '14 at 17:50

check if MX DNS resolution fails from your side or not with mxtoolbox.com

  • if you don't have MX results. exim should fallback to A record. cf exim FAQ (check Q0311 too)

use exim -bt -d-resolver user@example.org to diagnose exim mail routing

  • if yes. it means DNS resolution fails on your side.

run nslookup -type=MX example.org on your server. and check if you get MX records answers.

if not, try the same request but specify a well known nameserver, like google public dns: nslookup -type=MX example.org

you should now get some MX results, and it means your nameserver is not working properly. So you can change your resolv.conf to a nameserver that works properly (provider, google dns, what you want, ..) or setup your own

  • thank you! If I don't get any MX results for subdomain.example.com but get them for example.com, does it count? – hiirulainen Mar 31 '14 at 17:35
  • Not to my knowledge. the only one fallback is A record – exeral Mar 31 '14 at 18:18
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    one last question! if exim -bt -d-resolver user@example1.org succeeds but exim -bt -d-resolver user@example2.org fails, doesn't it mean that the problem is with example2.org and not with me? – hiirulainen Mar 31 '14 at 18:40
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    besides, when I do dig @ example2.org I get status: SERVFAIL and no answer section. And example2.org is the only domain I'm having such problems with, all my other addressees are able to get emails from me – hiirulainen Mar 31 '14 at 18:49
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    it means the nameserver of example2.org is unreachable, misconfigured. the problem is not on your side – exeral Mar 31 '14 at 19:30

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