I can no longer use TLS for Windows7 and Outlook

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Mark Constable

31 May 2020 31 May '20

7:36 a.m.

I currently use Ubuntu 20.04 with Dovecot 2.3.7.2 and OpenSSL 1.1.1f.

A few months ago there was an update to all these systems and since then I've had to talk W7 and old Mac clients through disabling ports 993/995 with TLS enabled back to ports 143/110 without SSL or they could not pick up email. Thunderbird users (ie; me) were unaffected.

Could anyone share a set of port 993/995 SSL settings known to work with Windows7 and Outlook16 using "dovecot -n|grep ^ssl_" please ?

Mine is currently...

ssl_ca =

I have commented out ssl_cipher_list, ssl_min_protocol and others to get back to whatever the defaults are so I am not simply guessing what the optimal settings would be to cover Win7 and up.

Yes I know Win7 is no longer supported but that does not help the 100s of older users I have that can't/won't upgrade their computers.

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Christian Kivalo

31 May 31 May

10:42 a.m.

On May 31, 2020 6:36:52 AM GMT+02:00, Mark Constable markc@renta.net wrote:

...

I currently use Ubuntu 20.04 with Dovecot 2.3.7.2 and OpenSSL 1.1.1f.

A few months ago there was an update to all these systems and since then I've had to talk W7 and old Mac clients through disabling ports 993/995 with TLS enabled back to ports 143/110 without SSL or they could not pick up email. Thunderbird users (ie; me) were unaffected.

Could anyone share a set of port 993/995 SSL settings known to work with Windows7 and Outlook16 using "dovecot -n|grep ^ssl_" please ? The best would be to upgrade your clients to a more current OS that supports those ciphers or change the mail client to something that ships it's own SSL/TLS implementation like Thunderbird.

I would under no circumstances allow access without TLS. You could also switch back to an older version of Ubuntu / openssl which in turn would allow the old clients to use SSL/TLS again. This would allow for an extended time period getting those clients to upgrade their OS.

...

Mine is currently...

ssl_ca =
I have commented out ssl_cipher_list, ssl_min_protocol and others to get back to whatever the defaults are so I am not simply guessing what the optimal settings would be to cover Win7 and up. Nevertheless you're up to a good amount of work, for Win7 I found this [1] that links to MSDN [2] where it states:

TLS 1.1 & TLS 1.2 are enabled by default on post Windows 8.1 releases. Prior to that they were disabled by default. So the administrators have to enable the settings manually via the registry. Refer this article on how to enable this protocols via registry: https://support.Microsoft.com/en-us/kb/187498

I haven't tested this as I don't have a Win7 installation available.

...

Yes I know Win7 is no longer supported but that does not help the 100s of older users I have that can't/won't upgrade their computers. There will probably be more problems relating to old OS and unsupported SSL/TLS versions in the future.

Good luck.

[1] https://support.globalsign.com/ssl/general-ssl/tls-protocol-compatibility [2] https://blogs.msdn.microsoft.com/kaushal/2011/10/02/support-for-ssltls-proto...

Christian Kivalo

＠lbutlr

11:41 a.m.

On 30 May 2020, at 22:36, Mark Constable markc@renta.net wrote:

...

993/995 with TLS enabled back to ports 143/110 without SSL or they could not pick up email. Thunderbird users (ie; me) were unaffected.

Insecure mail login is far too risky to allow. I don't even allow it within a LAN.

...

Could anyone share a set of port 993/995 SSL settings known to work with Windows7 and Outlook16 using "dovecot -n|grep ^ssl_" please ?

If the users cannot upgrade to an OS that works with TLS 1.2, then you need to either move them to a client that does its own TLS handling, or setup webmail (like Horde or Raoundcube).

Those clients on older machines are similarly going to have trouble accessing banks, health sites, or other secure logins as TLS 1.0 and 1.1 are not supported anymore. In fact, if it were not for the current pandemic, their browsers would already have lost TLS 1.0 and 1.1 abilities.

-- Margo: Give me a phaser and a red shirt. Male centurion: What?

Aki Tuomi

11:54 a.m.

Kostya Vasilyev

12:11 p.m.

On 5/31/20 11:54 AM, Aki Tuomi wrote:

...

...
On 31/05/2020 07:36 Mark Constable mailto:markc@renta.net> wrote:

I currently use Ubuntu 20.04 with Dovecot 2.3.7.2 and OpenSSL 1.1.1f.

A few months ago there was an update to all these systems and since then I've had to talk W7 and old Mac clients through disabling ports 993/995 with TLS enabled back to ports 143/110 without SSL or they could not pick up email. Thunderbird users (ie; me) were unaffected.

Could anyone share a set of port 993/995 SSL settings known to work with Windows7 and Outlook16 using "dovecot -n|grep ^ssl_" please ?

Mine is currently...

ssl_ca =
I have commented out ssl_cipher_list, ssl_min_protocol and others to get back to whatever the defaults are so I am not simply guessing what the optimal settings would be to cover Win7 and up.

Yes I know Win7 is no longer supported but that does not help the 100s of older users I have that can't/won't upgrade their computers.

ssl_min_protocol = TLSv1.0 ssl_ciphers = ALL:!LOW:!SSLv2:!EXP:!aNULL

if this works try tuning cipherlists to more secure value.

Aki Tuomi

Since you mention the newest Ubuntu version, it may (most likely) be necessary to enable TLS 1.0 / 1.1 in openssl as well. I ran into this with Debian 10 some time ago.

/etc/ssl/openssl.conf

[system_default_sect] -MinProtocol = TLSv1.2 +MinProtocol = TLSv1

In terms of Dovecot ciphers config, Windows should be happy with TLS_RSA_WITH_3DES_EDE_CBC_SHA which is less broken than the other older ciphers.

-- K

Benny Pedersen

5:29 p.m.

On 2020-05-31 11:11, Kostya Vasilyev wrote:

...

In terms of Dovecot ciphers config, Windows should be happy with TLS_RSA_WITH_3DES_EDE_CBC_SHA which is less broken than the other older ciphers.

lets hope that dovecot allow tls1 and still can disable tls1.1, tls 1.1 is weaker then tls 1.0

better solution is to drop windows 7, and old unsupported mac

Luuk

3 Jun 3 Jun

9:53 a.m.

On 31-5-2020 06:36, Mark Constable wrote:

...

I currently use Ubuntu 20.04 with Dovecot 2.3.7.2 and OpenSSL 1.1.1f.

A few months ago there was an update to all these systems and since then I've had to talk W7 and old Mac clients through disabling ports 993/995 with TLS enabled back to ports 143/110 without SSL or they could not pick up email. Thunderbird users (ie; me) were unaffected.

Could anyone share a set of port 993/995 SSL settings known to work with Windows7 and Outlook16 using "dovecot -n|grep ^ssl_" please ?

Mine is currently...

ssl_ca =
I have commented out ssl_cipher_list, ssl_min_protocol and others to get back to whatever the defaults are so I am not simply guessing what the optimal settings would be to cover Win7 and up.

Yes I know Win7 is no longer supported but that does not help the 100s of older users I have that can't/won't upgrade their computers.

Did you enable TLS1.2 in Windows 7?

https://support.microsoft.com/en-us/help/3140245/update-to-enable-tls-1-1-an...

(or, not tested on Windows 7: https://www.nartac.com/Products/IISCrypto/ )

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6 comments

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participants (7)

＠lbutlr
Aki Tuomi
Benny Pedersen
Christian Kivalo
Kostya Vasilyev
Luuk
Mark Constable