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JenlorFlag for United States of America

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Exchange SMTP 15 Second Timeout to Non-Exchange Environments

I got a weird one that we have been fighting for sometime now. In our Exchange 2013 environment, we are constantly running into SMTP timeout issues  when trying to send emails to non-Exchange environments. For instance, when Exchange goes to make that handshake, after a 15 second timeout, the connection just breaks and cant do anything outside of having the recipient white list us. Problem is, this is only happening to one client out of 100 that has the exact same setup. Its the timeout issue and cannot find anywhere to tell SMTP to go beyond that 15 second SMTP and wait until the other end proceeds with the greeting. Any ideas would be greatly appreciated.
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Amit
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What do you mean by non-exchange environment, as far as i know, Exchange keeps retrying to deliver mail to next hop. Refer: https://docs.microsoft.com/en-us/exchange/mail-flow/queues/message-intervals

I think you need focus on non-exchange environment more.
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The connection timesout from the Exchange server. We only have this issue when the recipient is using some sort of tarpitting technique with their SPAM device/software. I keep telling the client that there is really nothing that we can do and this issue is on the recipients side, but it happens enough for me rack my brains and wonder if I'm missing something. I agree 100% the issue is on the other end which we already know, but I'm trying to be a little more proactive so that this doesn't keep happening when the Exchange environment tries to emails somebody that is not using Exchange, but using some sort of POP service.
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Amit
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I know there's one on Exchange on the receive connector, but thats not where the problem resides. Its the outbound SMTP handshake that never occurs and times out and not the inbound. The inbound is fine.
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Thats what I kind of thought.
As @Amit said, there's no way you can fix an external server that's broken.
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