Hi,
The problem is that the Microsoft server does not support the cipher suites you’ve selected for your SSL cipher string.
The Microsoft SMTP server does not support any of the perfect forward secrecy suites at the 256 bit encryption level.
You can use the following cipher string to connect to Microsoft’s SMTP server with 256 bit encryption: (Configure>Security>Advanced)
ALL:!LOW:!EXP:!aNULL:!RC4:!3DES:!AES128:!RC4:!SEED:!CAMELLIA128:!IDEA:@STRENGTH
This will allow negotiation of the non-perfect forward secrecy suites that the Microsoft server supports at the 256 bit encryption level.