Keine Ahnung woran es hängt, schaue Dir mal 
https://github.com/jvehent/cipherscan an und eventuell mal für Deine Zielplattform bauen und testen. Oft liegt es an nicht richtig konfigurierten Servern die nicht richtig auf eine andere CipherSuite zurückfallen.
Basis für "old level", "intermediate level" und "modern level" ist die Empfehlung auf 
https://wiki.mozilla.org/Security/Server_Side_TLS
Für T-Online kommt dann so etwas heraus:
Code: Alles auswählen
doc@jessie:~/gitprojects/cipherscan [master] $ ./analyze.py -t secureimap.t-online.de:993
secureimap.t-online.de:993 has bad ssl/tls
Things that are bad:
* remove cipher ECDHE-RSA-RC4-SHA
Changes needed to match the old level:
* remove cipher ECDHE-RSA-RC4-SHA
* consider enabling SSLv3
* use a certificate with sha1WithRSAEncryption signature
* use DHE of 1024bits and ECC of 256bits
* consider enabling OCSP Stapling
Changes needed to match the intermediate level:
* remove cipher ECDHE-RSA-RC4-SHA
* consider using DHE of at least 2048bits and ECC of at least 256bits
* consider enabling OCSP Stapling
Changes needed to match the modern level:
* remove cipher ECDHE-RSA-RC4-SHA
* remove cipher DHE-RSA-CAMELLIA256-SHA
* remove cipher DHE-RSA-CAMELLIA128-SHA
* remove cipher AES256-GCM-SHA384
* remove cipher AES256-SHA256
* remove cipher AES256-SHA
* remove cipher AES128-GCM-SHA256
* remove cipher AES128-SHA256
* remove cipher AES128-SHA
* remove cipher DES-CBC3-SHA
* disable TLSv1
* use DHE of at least 2048bits and ECC of at least 256bits
* consider enabling OCSP Stapling
Aber Arcor sieht da auch nicht viel besser aus.
Code: Alles auswählen
doc@jessie:~/gitprojects/cipherscan [master] $ ./analyze.py -t imap.arcor.de:993
imap.arcor.de:993 has bad ssl/tls
Things that are bad:
* remove cipher RC4-SHA
Changes needed to match the old level:
* remove cipher RC4-SHA
* consider enabling TLSv1.1
* consider enabling TLSv1.2
* consider enabling SSLv3
* add cipher DES-CBC3-SHA
* consider enabling OCSP Stapling
* enforce server side ordering
Changes needed to match the intermediate level:
* remove cipher RC4-SHA
* consider enabling TLSv1.1
* consider enabling TLSv1.2
* consider using a SHA-256 certificate
* consider enabling OCSP Stapling
* enforce server side ordering
Changes needed to match the modern level:
* remove cipher AES256-SHA
* remove cipher CAMELLIA256-SHA
* remove cipher AES128-SHA
* remove cipher CAMELLIA128-SHA
* remove cipher RC4-SHA
* disable TLSv1
* consider enabling TLSv1.1
* consider enabling TLSv1.2
* use a SHA-256 certificate
* consider enabling OCSP Stapling
* enforce server side ordering
Und der CipherSuite Scan
Code: Alles auswählen
doc@jessie:~/gitprojects/cipherscan [master] $ ./cipherscan secureimap.t-online.de:993
.......................
Target: secureimap.t-online.de:993
prio  ciphersuite                  protocols              pfs_keysize                                                                                                                                                                                                          
1     ECDHE-RSA-AES256-GCM-SHA384  TLSv1.2                ECDH,P-384,384bits
2     ECDHE-RSA-AES256-SHA384      TLSv1.2                ECDH,P-384,384bits
3     ECDHE-RSA-AES256-SHA         TLSv1,TLSv1.1,TLSv1.2  ECDH,P-384,384bits
4     ECDHE-RSA-AES128-GCM-SHA256  TLSv1.2                ECDH,P-384,384bits
5     ECDHE-RSA-AES128-SHA256      TLSv1.2                ECDH,P-384,384bits
6     ECDHE-RSA-AES128-SHA         TLSv1,TLSv1.1,TLSv1.2  ECDH,P-384,384bits
7     ECDHE-RSA-RC4-SHA            TLSv1,TLSv1.1,TLSv1.2  ECDH,P-384,384bits
8     DHE-RSA-AES256-GCM-SHA384    TLSv1.2                DH,1024bits
9     DHE-RSA-AES256-SHA256        TLSv1.2                DH,1024bits
10    DHE-RSA-AES256-SHA           TLSv1,TLSv1.1,TLSv1.2  DH,1024bits
11    DHE-RSA-CAMELLIA256-SHA      TLSv1,TLSv1.1,TLSv1.2  DH,1024bits
12    DHE-RSA-AES128-GCM-SHA256    TLSv1.2                DH,1024bits
13    DHE-RSA-AES128-SHA256        TLSv1.2                DH,1024bits
14    DHE-RSA-AES128-SHA           TLSv1,TLSv1.1,TLSv1.2  DH,1024bits
15    DHE-RSA-CAMELLIA128-SHA      TLSv1,TLSv1.1,TLSv1.2  DH,1024bits
16    AES256-GCM-SHA384            TLSv1.2
17    AES256-SHA256                TLSv1.2
18    AES256-SHA                   TLSv1,TLSv1.1,TLSv1.2
19    AES128-GCM-SHA256            TLSv1.2
20    AES128-SHA256                TLSv1.2
21    AES128-SHA                   TLSv1,TLSv1.1,TLSv1.2
22    DES-CBC3-SHA                 TLSv1,TLSv1.1,TLSv1.2
Certificate: trusted, 2048 bit, sha256WithRSAEncryption signature
TLS ticket lifetime hint: 300
OCSP stapling: not supported
Server side cipher ordering