1 Topic by g40

  • g40
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Topic: Outlook 2010 SSL/TLS query

==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.6
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- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Yesterday a client who is using Outlook 2010 on an up-to-date Windows 10 starting seeing the following error, apparently without any Windows updates being applied.

Task 'x.y@z.com - Sending' reported error (0x800CCC1A) : 'Your server does not support the connection encryption type you have specified. Try changing the encryption method. Contact your mail server administrator or Internet service provider (ISP) for additional assistance.'

Outlook is configured to send via SMTP on port 587 using a TLS connection.

The entire server side installation has been stable since 0.9.6 was released and installed. So I am at a loss to explain what is happening.

I added SMTP/SSL support on port 465 as detailed here: https://docs.iredmail.org/enable.smtps.html. Outlook 2010 simply times out when connecting, whereas Outlook 2016 instances work without issue using 465/SSL for SMTP.

I can fall back to connecting via 110 if required but would prefer not. Are there any clues I should be searching here? The error seems to have appeared at random.

thx++

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2 Reply by Cthulhu (edited by Cthulhu 2022-10-18 07:51:49)

  • Cthulhu
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Re: Outlook 2010 SSL/TLS query

Tell you client to use a up to date version of outlook, we have year 2022 and not 2010, thus Outlook 2010 is neither maintained nor supported anymore

the server just refuses to use the encryption method outlook want's to use and thus the connection fails

So it is less "server does not support encrytion method", it is more "client does not support required encryption methods"


you can change the TLS settings:


https://ssl-config.mozilla.org/#server= … deline=5.6

But why should you make your whole server vulnerable because one client refuses to update his stuff?

3 Reply by g40

  • g40
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Re: Outlook 2010 SSL/TLS query

Cthulhu wrote:

Outlook 2010 is neither maintained nor supported anymore

Indeed. But it is more complex than that.

What I am trying to find out is why this error has appeared after years of stable operation.

4 Reply by g40

  • g40
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Re: Outlook 2010 SSL/TLS query

For anyone else looking for a quick fix to this problem see the very helpful https://docs.iredmail.org/additional.smtp.port.html which works with the most minimal changes to Outlook 2010 settings - use port 2525 and select 'None' for encryption method.

5 Reply by lmicetic (edited by lmicetic 2022-10-19 14:50:57)

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Re: Outlook 2010 SSL/TLS query

It's because of update KB5018410. If you uninstall it, it will work again. Waiting on Microsoft fix...

Just Google: smtp kb5018410

6 Reply by alexei.tarnakin

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Re: Outlook 2010 SSL/TLS query

Fix by Ms KB5020435