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We are using the Icewarp mail server with version: 11.1.2
Recently the mail server will indicate time out in the logs when some customers sent the email to us.

It is the same even thought I added the customer email server IP to the trust IP list.

Refer to below one example extracted from logs( below I use mycompany.com representing my company domain & customer.com representing customer domain)

xx.xx.xx.xx [0F9C] 09:33:04 Connected, local IP=
xx.xx.xx.xx [0F9C] 09:33:04 >>> 220 mycompany.com ESMTP IceWarp x64; Mon, 19 Jan 2015 09:33:04 +0800
xx.xx.xx.xx [0F9C] 09:33:04 <<< EHLO customer.com
xx.xx.xx.xx [0F9C] 09:33:04 >>> 250-xxx.com Hello customer.com [x.x.x.x], pleased to meet you.
xx.xx.xx.xx [0F9C] 09:33:04 <<< MAIL FROM:<Aifi@customer.com> SIZE=12894
xx.xx.xx.xx [0F9C] 09:33:04 >>> 250 2.1.0 <Aifi@customer.com>... Sender ok
xx.xx.xx.xx [0F9C] 09:33:04 <<< RCPT TO:<chlo@mycompany.com> ORCPT=rfc822;chlo@mycompany.com
xx.xx.xx.xx [0F9C] 09:33:04 >>> 250 2.1.5 <chlo@mycompany.com>... Recipient ok
xx.xx.xx.xx [0F9C] 09:33:04 <<< DATA
x.xx.xx.xx [0F9C] 09:33:04 >>> 354 Enter mail, end with "." on a line by itself
xx.xx.xx.xx [0F9C] 09:38:04 <<< 0 bytes (overall data transfer speed=0 B/s)
xx.xx.xx.xx [0F9C] 09:38:04 *** <Aifi@customer.com> <chlo@mycompany.com> 1 0 00:00:00 TIMEOUT 201501190933048591
xx.xx.xx.xx [0F9C] 09:38:04 Disconnected

Any suggestion.

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1 Answer 1

up vote 1 down vote accepted

The problem lies in your costumer.

Your server expect that the client (costumer) will sent email content after 354 Enter mail, end with "." on a line by itself. Unfortunately the client doesn't send any data after 5 minutes (09:33:04 -- 09:38:04) thus exceeding timeout from the server. Because server doesn't want to spend their resources on silent (and misbehaving) client, your server disconnect the connection.

Resourse: RFC5321

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In the begin, i also thought the issue is related to customer. But there are about more than 10 customers facing the same issue.Any advise. –  e0594cn Jan 20 at 3:22
Yes, your server was act according to standard. Without details about how the costumer behave, then we have no more data to troubleshooting it. Check if the costumer apps was really sending data, check also maybe some firewall drop the packet. –  masegaloeh Jan 20 at 3:24
Hi, all the related customer is coming from the same ISP. So we reported this issue to my ISP and it is solved. Thanks. –  e0594cn May 26 at 14:17

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