Synology MailPlus will not connect to SMTP relay on port 587, only works on 26, or 2525. Synology MailPlus will no...

Topic: Synology MailPlus will not connect to SMTP relay on port 587, only works on 26, or 2525.

Post Synology MailPlus will not connect to SMTP relay on port 587, only works on 26, or 2525.
by relink on 2020年9月11日

I am so close. Everything is functioning properly, I even get a good score on https://www.mail-tester.com/

My last issue now is that my Synology MailPlus server will not connect to the Dynu outbound relay on port 587. It works just fine on port 26, or port 2525. But I'm just not OK with using an unencrypted port.

If configured with port 587 the outgoing mail will sit in my servers Queue with an error that reads;

"connect to relay.dynu.com[168.235.105.136]:587: Connection timed out"

If configured with port 26, or 2525 everything works as expected, but from what I understand its not encrypted.


I have checked my firewall and I do not see any traffic to that port being blocked. I have also tested a connection to "relay.dynu.com" on port 587 from my firewall directly, and it seems to go through, so I'm not inclined to think the traffic is being blocked by my ISP either. Below is the output of that test;

Fri Sep 11 2020 09:30:54 GMT-0400 (Eastern Daylight Time) - Test Started
DNS fwd/rev mismatch: relay.dynu.com != relay.wiredblade.com
Test Successful
relay.dynu.com [168.235.105.136] 587 (submission) open
Fri Sep 11 2020 09:30:56 GMT-0400 (Eastern Daylight Time) - Test Completed

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I have also attached a screenshot of my relay settings. Also the check box for "Always use a secure connection (TLS)" is checked no matter what port im using...so that that possibly mean that my communication on port 26 or 2525 is encrypted? Is there any way to verify this?

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2020年10月25日 15:44
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