Hi Symantec,
We operate a cloud-based SaaS service which allows our users to manage marketing emails to their customers.
We have been finding that several recipients have been receiving multiple copies of email sent out, and upon investigating from our end, the connection to the messagelabs.com servers are either refusing connection, or simply timing out. That wouldn't necessarily be a problem as our mail server will simply mark the email as 'bounced', however, it would appear that the recipients are actually receiving some (if not all) of these emails.
You can see from a log extract below that our mail server attempts to connect to many different servers of yours and each one exhibits a similar problem. In many cases, even though it claims to accept the message, the session simply times out after 60 seconds, thus resulting in another retry.
I have checked that our outbound IP (in this case 46.37.186.167) is not listed on your blocklist (http://ipremoval.sms.symantec.com/lookup/).
Log extract:
[2017.09.12] 11:34:04 [11411] Sending remote mail for bounce-10-1259-6749-6638686-177@clarity-marketing.com
[2017.09.12] 11:34:04 [11411] Initiating connection to 216.82.242.34
[2017.09.12] 11:34:04 [11411] Connecting to 216.82.242.34:25 (Id: 1)
[2017.09.12] 11:34:04 [11411] Binding to local IP 172.27.226.13:0 (Id: 1)
[2017.09.12] 11:34:04 [11411] Connection to 216.82.242.34:25 from 172.27.226.13:55517 succeeded (Id: 1)
[2017.09.12] 11:34:04 [11411] RSP: 220 ***************************************
[2017.09.12] 11:34:04 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:34:04 [11411] RSP: 250-server-9.tower-73.messagelabs.com
[2017.09.12] 11:34:04 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:34:04 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:34:04 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:34:04 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:34:04 [11411] RSP: 250 OK
[2017.09.12] 11:34:04 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:34:05 [11411] RSP: 250 OK
[2017.09.12] 11:34:05 [11411] CMD: DATA
[2017.09.12] 11:34:05 [11411] RSP: 354 go ahead
[2017.09.12] 11:35:05 [11411] The smtp session has timed out.
[2017.09.12] 11:35:05 [11411] Initiating connection to 216.82.251.37
[2017.09.12] 11:35:05 [11411] Connecting to 216.82.251.37:25 (Id: 2)
[2017.09.12] 11:35:05 [11411] Binding to local IP 172.27.226.13:0 (Id: 2)
[2017.09.12] 11:35:05 [11411] Connection to 216.82.251.37:25 from 172.27.226.13:55773 succeeded (Id: 2)
[2017.09.12] 11:35:05 [11411] RSP: 220 ****************************************
[2017.09.12] 11:35:05 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:35:05 [11411] RSP: 250-server-3.tower-153.messagelabs.com
[2017.09.12] 11:35:05 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:35:05 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:35:05 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:35:05 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:35:05 [11411] RSP: 250 OK
[2017.09.12] 11:35:05 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:35:06 [11411] RSP: 250 OK
[2017.09.12] 11:35:06 [11411] CMD: DATA
[2017.09.12] 11:35:06 [11411] RSP: 354 go ahead
[2017.09.12] 11:36:06 [11411] The smtp session has timed out.
[2017.09.12] 11:36:06 [11411] Initiating connection to 216.82.242.37
[2017.09.12] 11:36:06 [11411] Connecting to 216.82.242.37:25 (Id: 3)
[2017.09.12] 11:36:06 [11411] Binding to local IP 172.27.226.13:0 (Id: 3)
[2017.09.12] 11:36:06 [11411] Connection to 216.82.242.37:25 from 172.27.226.13:56185 succeeded (Id: 3)
[2017.09.12] 11:36:06 [11411] RSP: 220 ****************************************
[2017.09.12] 11:36:06 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:36:06 [11411] RSP: 250-server-16.tower-99.messagelabs.com
[2017.09.12] 11:36:06 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:36:06 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:36:06 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:36:06 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:36:06 [11411] RSP: 250 OK
[2017.09.12] 11:36:06 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:36:06 [11411] RSP: 250 OK
[2017.09.12] 11:36:06 [11411] CMD: DATA
[2017.09.12] 11:36:07 [11411] RSP: 354 go ahead
[2017.09.12] 11:37:07 [11411] The smtp session has timed out.
[2017.09.12] 11:37:07 [11411] Initiating connection to 216.82.250.51
[2017.09.12] 11:37:07 [11411] Connecting to 216.82.250.51:25 (Id: 4)
[2017.09.12] 11:37:07 [11411] Binding to local IP 172.27.226.13:0 (Id: 4)
[2017.09.12] 11:37:07 [11411] Connection to 216.82.250.51:25 from 172.27.226.13:56510 succeeded (Id: 4)
[2017.09.12] 11:37:07 [11411] RSP: 220 *****************************************
[2017.09.12] 11:37:07 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:37:07 [11411] RSP: 250-server-13.tower-108.messagelabs.com
[2017.09.12] 11:37:07 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:37:07 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:37:07 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:37:07 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:37:07 [11411] RSP: 250 OK
[2017.09.12] 11:37:07 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:37:08 [11411] RSP: 250 OK
[2017.09.12] 11:37:08 [11411] CMD: DATA
[2017.09.12] 11:37:08 [11411] RSP: 354 go ahead
[2017.09.12] 11:38:08 [11411] The smtp session has timed out.
[2017.09.12] 11:38:08 [11411] Initiating connection to 216.82.242.131
[2017.09.12] 11:38:08 [11411] Connecting to 216.82.242.131:25 (Id: 5)
[2017.09.12] 11:38:08 [11411] Binding to local IP 172.27.226.13:0 (Id: 5)
[2017.09.12] 11:38:09 [11411] Exception connecting to 216.82.242.131 (Id: 5)
[2017.09.12] 11:38:09 [11411] System.Net.Sockets.SocketException (0x80004005): No connection could be made because the target machine actively refused it 216.82.242.131:25
[2017.09.12] 11:38:09 [11411] Binding to local ip '172.27.226.13' failed. Switched binding to primary local ip.
[2017.09.12] 11:38:09 [11411] Connecting to 216.82.242.131:25 (Id: 6)
[2017.09.12] 11:38:09 [11411] Connection to 216.82.242.131:25 from 172.27.226.9:56821 succeeded (Id: 6)
[2017.09.12] 11:38:09 [11411] RSP: 220 ***************************************
[2017.09.12] 11:38:09 [11411] CMD: EHLO mail.claritygo.com
[2017.09.12] 11:38:10 [11411] RSP: 250-server-6.tower-76.messagelabs.com
[2017.09.12] 11:38:10 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:38:10 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:38:10 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:38:10 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:38:10 [11411] RSP: 250 OK
[2017.09.12] 11:38:10 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:38:10 [11411] RSP: 250 OK
[2017.09.12] 11:38:10 [11411] CMD: DATA
[2017.09.12] 11:38:10 [11411] RSP: 354 go ahead
[2017.09.12] 11:39:10 [11411] The smtp session has timed out.
[2017.09.12] 11:39:10 [11411] Initiating connection to 216.82.241.195
[2017.09.12] 11:39:10 [11411] Connecting to 216.82.241.195:25 (Id: 7)
[2017.09.12] 11:39:10 [11411] Binding to local IP 172.27.226.13:0 (Id: 7)
[2017.09.12] 11:39:10 [11411] Connection to 216.82.241.195:25 from 172.27.226.13:57076 succeeded (Id: 7)
[2017.09.12] 11:39:10 [11411] RSP: 220 *****************************************
[2017.09.12] 11:39:10 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:39:10 [11411] RSP: 250-server-10.tower-119.messagelabs.com
[2017.09.12] 11:39:10 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:39:10 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:39:10 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:39:10 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:39:11 [11411] RSP: 250 OK
[2017.09.12] 11:39:11 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:39:11 [11411] RSP: 250 OK
[2017.09.12] 11:39:11 [11411] CMD: DATA
[2017.09.12] 11:39:11 [11411] RSP: 354 go ahead
[2017.09.12] 11:40:11 [11411] The smtp session has timed out.
[2017.09.12] 11:40:11 [11411] Initiating connection to 216.82.250.83
[2017.09.12] 11:40:11 [11411] Connecting to 216.82.250.83:25 (Id: 8)
[2017.09.12] 11:40:11 [11411] Binding to local IP 172.27.226.13:0 (Id: 8)
[2017.09.12] 11:40:11 [11411] Connection to 216.82.250.83:25 from 172.27.226.13:57383 succeeded (Id: 8)
[2017.09.12] 11:40:11 [11411] RSP: 220 ****************************************
[2017.09.12] 11:40:11 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:40:11 [11411] RSP: 250-server-5.tower-120.messagelabs.com
[2017.09.12] 11:40:11 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:40:11 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:40:11 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:40:11 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:40:12 [11411] RSP: 250 OK
[2017.09.12] 11:40:12 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:40:12 [11411] RSP: 250 OK
[2017.09.12] 11:40:12 [11411] CMD: DATA
[2017.09.12] 11:40:12 [11411] RSP: 354 go ahead
[2017.09.12] 11:41:12 [11411] The smtp session has timed out.
[2017.09.12] 11:41:12 [11411] Initiating connection to 216.82.251.35
[2017.09.12] 11:41:12 [11411] Connecting to 216.82.251.35:25 (Id: 9)
[2017.09.12] 11:41:12 [11411] Binding to local IP 172.27.226.13:0 (Id: 9)
[2017.09.12] 11:41:12 [11411] Connection to 216.82.251.35:25 from 172.27.226.13:57665 succeeded (Id: 9)
[2017.09.12] 11:41:12 [11411] RSP: 220 ****************************************
[2017.09.12] 11:41:12 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:41:13 [11411] RSP: 250-server-3.tower-151.messagelabs.com
[2017.09.12] 11:41:13 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:41:13 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:41:13 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:41:13 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:41:13 [11411] RSP: 250 OK
[2017.09.12] 11:41:13 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:41:13 [11411] RSP: 250 OK
[2017.09.12] 11:41:13 [11411] CMD: DATA
[2017.09.12] 11:41:13 [11411] RSP: 354 go ahead
[2017.09.12] 11:42:13 [11411] The smtp session has timed out.
[2017.09.12] 11:42:13 [11411] Initiating connection to 216.82.250.99
[2017.09.12] 11:42:13 [11411] Connecting to 216.82.250.99:25 (Id: 10)
[2017.09.12] 11:42:13 [11411] Binding to local IP 172.27.226.13:0 (Id: 10)
[2017.09.12] 11:42:14 [11411] Connection to 216.82.250.99:25 from 172.27.226.13:57915 succeeded (Id: 10)
[2017.09.12] 11:42:14 [11411] RSP: 220 ****************************************
[2017.09.12] 11:42:14 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:42:14 [11411] RSP: 250-server-7.tower-126.messagelabs.com
[2017.09.12] 11:42:14 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:42:14 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:42:14 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:42:14 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:42:14 [11411] RSP: 250 OK
[2017.09.12] 11:42:14 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:42:14 [11411] RSP: 250 OK
[2017.09.12] 11:42:14 [11411] CMD: DATA
[2017.09.12] 11:42:14 [11411] RSP: 354 go ahead
[2017.09.12] 11:43:15 [11411] The smtp session has timed out.
[2017.09.12] 11:43:15 [11411] Initiating connection to 216.82.251.36
[2017.09.12] 11:43:15 [11411] Connecting to 216.82.251.36:25 (Id: 11)
[2017.09.12] 11:43:15 [11411] Binding to local IP 172.27.226.13:0 (Id: 11)
[2017.09.12] 11:43:15 [11411] Connection to 216.82.251.36:25 from 172.27.226.13:58223 succeeded (Id: 11)
[2017.09.12] 11:43:15 [11411] RSP: 220 ****************************************
[2017.09.12] 11:43:15 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:43:15 [11411] RSP: 250-server-8.tower-152.messagelabs.com
[2017.09.12] 11:43:15 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:43:15 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:43:15 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:43:15 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:43:15 [11411] RSP: 250 OK
[2017.09.12] 11:43:15 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:43:15 [11411] RSP: 250 OK
[2017.09.12] 11:43:15 [11411] CMD: DATA
[2017.09.12] 11:43:16 [11411] RSP: 354 go ahead
[2017.09.12] 11:44:16 [11411] The smtp session has timed out.
[2017.09.12] 11:44:16 [11411] Initiating connection to 216.82.242.147
[2017.09.12] 11:44:16 [11411] Connecting to 216.82.242.147:25 (Id: 12)
[2017.09.12] 11:44:16 [11411] Binding to local IP 172.27.226.13:0 (Id: 12)
[2017.09.12] 11:44:16 [11411] Connection to 216.82.242.147:25 from 172.27.226.13:58495 succeeded (Id: 12)
[2017.09.12] 11:44:16 [11411] RSP: 220 ****************************************
[2017.09.12] 11:44:16 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:44:16 [11411] RSP: 250-server-11.tower-95.messagelabs.com
[2017.09.12] 11:44:16 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:44:16 [11411] RSP: 250-PIPELINING
[2017.09.12] 11:44:16 [11411] RSP: 250 8BITMIME
[2017.09.12] 11:44:16 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:44:16 [11411] RSP: 250 OK
[2017.09.12] 11:44:16 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:44:16 [11411] RSP: 250 OK
[2017.09.12] 11:44:16 [11411] CMD: DATA
[2017.09.12] 11:44:17 [11411] RSP: 354 go ahead
[2017.09.12] 11:45:17 [11411] The smtp session has timed out.
[2017.09.12] 11:45:17 [11411] Initiating connection to 216.82.251.230
[2017.09.12] 11:45:17 [11411] Connecting to 216.82.251.230:25 (Id: 13)
[2017.09.12] 11:45:17 [11411] Binding to local IP 172.27.226.13:0 (Id: 13)
[2017.09.12] 11:45:17 [11411] Connection to 216.82.251.230:25 from 172.27.226.13:58756 succeeded (Id: 13)
[2017.09.12] 11:45:17 [11411] RSP: 220 *****************************************
[2017.09.12] 11:45:17 [11411] CMD: EHLO mail3.claritygo.com
[2017.09.12] 11:45:18 [11411] RSP: 250-server-12.tower-555.messagelabs.com says EHLO to 46.37.186.167:58756
[2017.09.12] 11:45:18 [11411] RSP: 250-8BITMIME
[2017.09.12] 11:45:18 [11411] RSP: 250-XXXXXXXA
[2017.09.12] 11:45:18 [11411] RSP: 250 PIPELINING
[2017.09.12] 11:45:18 [11411] CMD: MAIL FROM:<bounce-10-1259-6749-6638686-177@clarity-marketing.com>
[2017.09.12] 11:45:18 [11411] RSP: 250 2.0.0 MAIL FROM accepted
[2017.09.12] 11:45:18 [11411] CMD: RCPT TO:<sian.dutton@havaspeople.com>
[2017.09.12] 11:45:18 [11411] RSP: 421 Service Temporarily Unavailable
[2017.09.12] 11:45:18 [11411] CMD: QUIT