We forward our emails via Sophos to Socket Labs Smart Host service. The service itself works well, however, all emails we send are being sent twice.
The mails server we send form is an Exchange 2019 server, if we send directly from that server to Socket Labs, the emails only go once.
If we send via Sophos UTM the recipient receives two copies of the email.
In the Email Manager view we see the following entries.
Message ID 1qJ2aO-0002rb-7h
2023-07-11 09:54:41 H=east.in.socketlabs.com [142.0.180.14]:587: Remote host closed connection in response to end of data
2023-07-11 09:54:41 mxxxxx@gmail.com R=smarthost_route T=smarthost_smtp defer (-18) H=east.in.socketlabs.com [142.0.180.14]:587: Remote host closed connection in response to end of data
2023-07-11 09:57:01 mxxxxx@gmail.com: smarthost_smtp transport succeeded to 142.0.180.14 (east.in.socketlabs.com)
If we look in the detailed logs we get:
2023:07:11-09:54:40 firewall smtpd[11011]: SCANNER[11011]: 1qJ2aO-0002rb-7h <= mark@***********.com R=1qJ2aL-0002rY-15 P=INPUT S=100791
2023:07:11-09:54:40 firewall smtpd[11011]: SCANNER[11011]: id="1000" severity="info" sys="SecureMail" sub="smtp" name="email passed" srcip="192.168.1.217" from="mark@*********.com" to="*******@gmail.com" subject="Test from Exchange" queueid="1qJ2aO-0002rb-7h" size="100791"
2023:07:11-09:54:41 firewall exim-out[11017]: 2023-07-11 09:54:41 1qJ2aO-0002rb-7h H=east.in.socketlabs.com [142.0.180.14]:587: Remote host closed connection in response to end of data
2023:07:11-09:54:41 firewall exim-out[11016]: 2023-07-11 09:54:41 1qJ2aO-0002rb-7h == m*********@gmail.com R=smarthost_route T=smarthost_smtp defer (-18) H=east.in.socketlabs.com [142.0.180.14]:587: Remote host closed connection in response to end of data
2023:07:11-09:55:00 firewall exim-out[11031]: 2023-07-11 09:55:00 1qJ2aO-0002rb-7h == m********@gmail.com R=smarthost_route T=smarthost_smtp defer (-54): retry time not reached for any host for 'gmail.com'
2023:07:11-09:56:00 firewall exim-out[11139]: 2023-07-11 09:56:00 1qJ2aO-0002rb-7h == m*********@gmail.com R=smarthost_route T=smarthost_smtp defer (-54): retry time not reached for any host for 'gmail.com'
2023:07:11-09:57:01 firewall exim-out[11199]: 2023-07-11 09:57:01 1qJ2aO-0002rb-7h => m********@gmail.com P=<prvs=055626b7f7=mark@***********.com> R=smarthost_route T=smarthost_smtp H=east.in.socketlabs.com [142.0.180.14]:587 A=server_login C="250 2.0.0 Message received and queued as 750002721315."
2023:07:11-09:57:01 firewall exim-out[11199]: 2023-07-11 09:57:01 1qJ2aO-0002rb-7h Completed
We have checked the logs at the Socket Labs end, and they have confirmed that we are sending a QUIT before they have sent the 250 OK. But they have actually received the email, just not finished processing it yet.
As I send, when send from Exchange Server 2019 to SocketLabs using the same host and account details it works fine.
What would cause us to send a QUIT before receiving the 250 OK? Is it possible to set a delay in sending it? Has anyone else experienced this problem?
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