Topic: 450 Temporary address resolution failure error

[Peasant]

I had a report of emails sent to a Koozali server being bounced back with the error:
'550 5.4.300 Message expired -> 450 Temporary address resolution failure (#4.4.3)'

Searching the forums came up with this thread:
https://forums.contribs.org/index.php?topic=53062.0

and by adding the sender to the whitelist the problem disappeared. However, I was curious, so went to the qsmtpd log files and found the following. The sender is myfarm.co.uk, and the server is mydealer.co.uk:

Code: [Select]

2021-05-23 12:32:04.044330500 30950 Accepted connection 0/40 from 40.107.10.49 / mail-eopbgr100049.outbound.protection.outlook.com
2021-05-23 12:32:04.044412500 30950 Connection from mail-eopbgr100049.outbound.protection.outlook.com [40.107.10.49]
2021-05-23 12:32:05.241408500 30950 (connect) earlytalker: pass, not spontaneous
2021-05-23 12:32:05.242557500 30950 (connect) relay: skip, no match
2021-05-23 12:32:05.243017500 30950 220 yoda.mydealer.co.uk ESMTP
2021-05-23 12:32:05.273477500 30950 dispatching EHLO GBR01-LO2-obe.outbound.protection.outlook.com
2021-05-23 12:32:05.274508500 30950 (ehlo) helo: pass
2021-05-23 12:32:05.275316500 30950 250-mydealer.co.uk Hi mail-eopbgr100049.outbound.protection.outlook.com [40.107.10.49]
2021-05-23 12:32:05.275318500 30950 250-PIPELINING
2021-05-23 12:32:05.275349500 30950 250-8BITMIME
2021-05-23 12:32:05.275364500 30950 250-SIZE 45000000
2021-05-23 12:32:05.275378500 30950 250 STARTTLS
2021-05-23 12:32:05.306432500 30950 dispatching STARTTLS
2021-05-23 12:32:05.306532500 30950 220 Go ahead with TLS
2021-05-23 12:32:05.413580500 30950 (unrecognized_command) tls: TLS setup returning
2021-05-23 12:32:05.446897500 30950 dispatching EHLO GBR01-LO2-obe.outbound.protection.outlook.com
2021-05-23 12:32:05.447566500 30950 (ehlo) helo: pass
2021-05-23 12:32:05.448026500 30950 250-mydealer.co.uk Hi mail-eopbgr100049.outbound.protection.outlook.com [40.107.10.49]
2021-05-23 12:32:05.448028500 30950 250-PIPELINING
2021-05-23 12:32:05.448053500 30950 250-8BITMIME
2021-05-23 12:32:05.448088500 30950 250-SIZE 45000000
2021-05-23 12:32:05.448088500 30950 250 AUTH PLAIN LOGIN
2021-05-23 12:32:05.482682500 30950 dispatching MAIL FROM:<claire@myfarm.co.uk> SIZE=17098
2021-05-23 12:32:36.000090500 30950 (mail) resolvable_fromhost: karma -1 (-1)
2021-05-23 12:32:36.000091500 30950 (mail) resolvable_fromhost: myfarm.co.uk has no MX
2021-05-23 12:33:38.000074500 30950 (mail) resolvable_fromhost: fail, query for myfarm.co.uk,  query timed out
2021-05-23 12:33:38.000075500 30950 (mail) resolvable_fromhost: fail, missing result
2021-05-23 12:33:38.000255500 30950 (deny) logging::logterse: ` 40.107.10.49 mail-eopbgr100049.outbound.protection.outlook.com GBR01-LO2-obe.outbound.protection.outlook.com resolvable_fromhost 902 Temporary address resolution failure (#4.4.3) msg denied before queued
2021-05-23 12:33:38.000322500 30950 denysoft mail from <claire@myfarm.co.uk> (Temporary address resolution failure (#4.4.3))
2021-05-23 12:33:38.000334500 30950 450 Temporary address resolution failure (#4.4.3)
2021-05-23 12:33:38.000600500 30950 dispatching RCPT TO:<george@mydealer.co.uk>
2021-05-23 12:33:38.000698500 30950 503 Use MAIL before RCPT
2021-05-23 12:33:38.000852500 30950 dispatching RCPT TO:<accounts@mydealer.co.uk>
2021-05-23 12:33:38.000917500 30950 503 Use MAIL before RCPT
2021-05-23 12:33:38.104286500 30950 dispatching QUIT
2021-05-23 12:33:38.104503500 30950 Lost connection to client, cannot send response.
2021-05-23 12:33:38.104529500 30950 click, disconnecting
2021-05-23 12:33:38.846133500 2564 cleaning up after 30950
I'm no DNS expert, but it looks like myfarm.co.uk have errors with the MX record. They use Office365 from what I can see.

Does anyone have any thoughts? Thanks.

[mmccarn]

2021-05-23 12:32:05.482682500 30950 dispatching MAIL FROM:<claire@myfarm.co.uk> SIZE=17098
2021-05-23 12:32:36.000090500 30950 (mail) resolvable_fromhost: karma -1 (-1)
2021-05-23 12:32:36.000091500 30950 (mail) resolvable_fromhost: myfarm.co.uk has no MX
2021-05-23 12:33:38.000074500 30950 (mail) resolvable_fromhost: fail, query for myfarm.co.uk,  query timed out

I'm pretty sure this is saying that the SME server timed out trying to resolve 'myfarm.co.uk'

I've never seen or heard of this affecting DNS particularly, but if nslookup myfarm.co.uk works from the SME itself you should check the 'PMTU' value between your SME and the DNS server(s) you're using.  There's a wiki section about PMTU and qpsmtpd connection timeouts.

[Peasant]

Thanks. The fact that it was working fine, and then has suddenly stopped made me wonder about something like this.