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IMAP Roundtrip originating from external



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So this is going to sound backward from how the round-trip IMAP/POP3 sensors are typically used...but here is what I want to do:

We have internal Exchange servers that do not have IMAP or POP3 enabled. We have no need to enable those services and do not want to for the sole reason of round-trip mail monitoring. Is it possible to setup either of these sensors to use a Gmail account as the originating mailbox/SMTP server, send the message to our on-premise Exchange with an auto reply back to Gmail, and then have the sensor check the gmail box?

I want the sensor to monitor mail flow from Gmail to on premise and back so I want to use their SMTP server (Gmail -> SPAM filter -> Exchange -> Gmail. If I use our internal one I would only test the outbound connection (internal SMTP -> internal Exchange -> Gmail).

So far I only get errors when trying to make the SMTP connection. I created a device called and tried to configure it to point to Gmail's ports as defined at but have had no luck getting a connection. In the sensor log I only see "Connection to SMTP Server: Unexpected connection drop (code: PE039)".

I am pretty sure the IMAP part of the connection will work fine once it gets past the SMTP connection and sends the message.

gmail roundtrip smtp

Created on Nov 18, 2016 4:48:45 PM by  rdertien (0) 1

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Hi there,

Please make sure that you have enabled the "Less secure apps" option within the GMail-Account as described on the following site: Touchmail. Afterwards you should be able to send a mail via GMail.

Created on Nov 21, 2016 10:10:43 AM by  Dariusz Gorka [Paessler Support]

Last change on Nov 21, 2016 10:10:52 AM by  Dariusz Gorka [Paessler Support]

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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.