I would expect it to be resolved by upgrading the software on your mail server, 
yes. 

-Philip 

On April 14, 2016 7:19:51 PM GMT+01:00, Joakim Hirsch <[email protected]> 
wrote:
>Thank you Philip,
>
>As you may have guessed I don't know an awful lot about these things. 
>Your answer helped me tremendously though. I started to look into why
>my 
>mail server doesn't support the more recent protocols. It turned out 
>that the NAS does, but not the mail server. Apparently they use 
>different certificates. So I need to replace the mail server's cert 
>(it's the default one that came with the installation) with something 
>that will enable TLS1.1 and 1.2. If I'm totally off here, please tell 
>me. Otherwise I thank you for your help.
>
>Best regards,
>Joa
>
>Den 2016-04-14 kl. 09:08, skrev Philip Whitehouse:
>> Android 6.0 uses BoringSSL which enforces a minimum default
>DiffieHelman length (BAD_DH_P_LENGTH) to mitigate the LogJam attack.
>>
>> I would guess that Gmail disables this. We probably could but we
>don't. I'm not sure it's a good idea.
>>
>> We have existing issues open to improve the errors we give - I'll
>make sure this instance is covered.
>>
>> I think upgrading the software your email server runs should fix this
>- the servers use some default parameters I believe.
>>
>> If you wanted to change your setup you definitely could improve it -
>e.g. SSLv3 is broken and all clients should refuse to use it.
>>
>>
>> On April 14, 2016 7:36:21 AM GMT+01:00, Joa H <[email protected]>
>wrote:
>>> Hi
>>>
>>> K-9 won´t connect after upgrading to Android 6.0, I get the below
>>> exception. This didn't happen before. Incidentally MailWise also
>does
>>> not
>>> work since then. I tried Gmail and that works, so I'm not sure where
>>> the
>>> problem lies. I've tried to find something on this problem, but
>haven't
>>>
>>> found much. There are suggestions that it might be the server not
>>> supporting necessary protocols or cipher suites, but why then does
>>> Gmail
>>> work?
>>>
>>> My IMAP server has a (since 2011 expired) self signed certificate
>>> (which
>>> worked fine til now). An SSL check reveals that TLS1.0 and SSLv3 are
>>> supported and the following ciphers:
>>> TLS_RSA_EXPORT_WITH_RC4_40_MD5 (0x0003)
>>> TLS_RSA_WITH_RC4_128_MD5 (0x0004)
>>> TLS_RSA_WITH_RC4_128_SHA (0x0005)
>>> TLS_RSA_EXPORT_WITH_DES40_CBC_SHA (0x0008)
>>> TLS_RSA_WITH_DES_CBC_SHA (0x0009)
>>> TLS_RSA_WITH_3DES_EDE_CBC_SHA (0x000A)
>>> TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA (0x0014)
>>> TLS_DHE_RSA_WITH_DES_CBC_SHA (0x0015)
>>> TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA (0x0016)
>>> TLS_RSA_WITH_AES_128_CBC_SHA (0x002F)
>>> TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
>>>
>>> I would be grateful for any tips.
>>>
>>> The exception:
>>>
>>> K9-Mail version: 5.010
>>> Device make: Sony
>>> Device model: E6653
>>> Android version: 6.0
>>>
>>> com.fsck.k9.mail.MessagingException: IO Error
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapFolder.ioExceptionHandler(ImapStore.java:2208)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapFolder.internalOpen(ImapStore.java:947)
>>>     at
>>> com.fsck.k9.mail.store.ImapStore$ImapFolder.open(ImapStore.java:867)
>>>     at
>>>
>com.fsck.k9.controller.MessagingController.synchronizeMailboxSynchronous(MessagingController.java:1041)
>>>     at
>>>
>com.fsck.k9.controller.MessagingController.access$400(MessagingController.java:111)
>>>     at
>>>
>com.fsck.k9.controller.MessagingController$8.run(MessagingController.java:934)
>>>     at
>>>
>com.fsck.k9.controller.MessagingController.run(MessagingController.java:435)
>>>     at java.lang.Thread.run(Thread.java:818)
>>> Caused by: javax.net.ssl.SSLHandshakeException: Handshake failed
>>>     at
>>>
>com.android.org.conscrypt.OpenSSLSocketImpl.startHandshake(OpenSSLSocketImpl.java:396)
>>>     at
>>>
>com.android.org.conscrypt.OpenSSLSocketImpl.waitForHandshake(OpenSSLSocketImpl.java:629)
>>>     at
>>>
>com.android.org.conscrypt.OpenSSLSocketImpl.getInputStream(OpenSSLSocketImpl.java:591)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapConnection.open(ImapStore.java:2460)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapConnection.sendCommand(ImapStore.java:2872)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapConnection.executeSimpleCommand(ImapStore.java:2921)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapConnection.executeSimpleCommand(ImapStore.java:2902)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapFolder.executeSimpleCommand(ImapStore.java:858)
>>>     at
>>>
>com.fsck.k9.mail.store.ImapStore$ImapFolder.internalOpen(ImapStore.java:904)
>>>     ... 6 more
>>> Caused by: javax.net.ssl.SSLProtocolException: SSL handshake
>aborted:
>>> ssl=0x7f41039300: Failure in SSL library, usually a protocol error
>>> error:100c1069:SSL
>>> routines:ssl3_get_server_key_exchange:BAD_DH_P_LENGTH
>>> (external/boringssl/src/ssl/s3_clnt.c:1193 0x7f73563518:0x00000000)
>>>     at com.android.org.conscrypt.NativeCrypto.SSL_do_handshake(Native
>>> Method)
>>>     at
>>>
>com.android.org.conscrypt.OpenSSLSocketImpl.startHandshake(OpenSSLSocketImpl.java:324)
>>>     ... 14 more
>>>
>>>
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>> Best regards,
>>
>> Philip Whitehouse
>
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Best regards,

Philip Whitehouse

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