We are having a incoming mail delivery delays.
Exchange 2013 CU3 with separate CAS and MBX roles
Puremessage spam filtering on MBX server role
Allowed maximum attachment size to send/receive - 35 MB
1. Email works internally
2. Receiving and sending emails with out attachments is instantaneous to and from external parties.
3. Receiving emails with attachments from external senders (Ex: gmail) over 3 MB get delayed. Sometimes by 10-20 hours
4. Sending emails from the organization to external senders (Ex: gmail) with attachments over 3 MB is instantaneous.
So the problem we are facing is receiving emails with attachments from external senders. “Some” of these get delivered after long delays but many go missing.
Following is an email header analysis of a delayed message.
Hop Delay from by with time (UTC)
1 * 000s-ex-mbx-qs3.AAA.edu.au 000s-ex-hub-np2.AAA.edu.au mapi 3/6/2014 12:24:12 AM
2 * 000S-EX-HUB-NP2.AAA.edu.au 172.22.174.21 000s-ex-tmg-np2.AAA.edu.au 172.22.174.5 Microsoft SMTP Server (TLS) 3/6/2014 12:23:58 AM
3 57 seconds 000s-ex-tmg-np2.AAA.edu.au 22.214.171.124 CH1EHSMHS001.bigfish.com 10.43.70.1 Microsoft SMTP Server (TLS) 3/6/2014 12:24:55 AM
4 41 seconds CH1EHSMHS001.bigfish.com 10.43.68.231 mail13-ch1.bigfish.com ESMTP 3/6/2014 12:25:36 AM
5 3 seconds mail13-ch1 127.0.0.1 mail13-ch1 3/6/2014 12:25:39 AM
6 3 seconds mail13-ch1 127.0.0.1 mail13-ch1-R.bigfish.com ESMTP 3/6/2014 12:25:42 AM
7 0 seconds mail13-ch1-R.bigfish.com 10.43.68.246 CH1EHSOBE005.bigfish.com 10.43.70.55 Microsoft SMTP Server 3/6/2014 12:25:42 AM
8 20 hour ch1outboundpool.messaging.microsoft.com 126.96.36.199 CAS01.YYYYY.org.au 10.0.100.103 Microsoft SMTP Server (TLS) 3/6/2014 7:57:17 PM
9 2 minutes CAS01.YYYYY.org.au 10.0.100.211 MBX01.YYYYY.org.au 10.0.100.125 Microsoft SMTP Server (TLS) 3/6/2014 7:59:40 PM
10 * MBX01.YYYYY.org.au 10.0.100.125
If you notice , Hop number 8 took 20 hours to complete.
Test results form MX toolbox
SMTP Transaction Time 5.881 seconds
SMTP Reverse Banner Check OK – YYY.YYY.YYY.YYY resolves to mail.YYYYY.org.au
SMTP Reverse DNS Mismatch OK - Reverse DNS matches SMTP Banner
SMTP TLS OK - Supports TLS.
SMTP Connection Time 1.092 seconds - Good on Connection time
SMTP Open Relay OK - Not an open relay.
Does anyone has any idea about the possible cause of this receive delay.
Any suggestion would be greatly appreciated.