#9 Added AuthType property with support for CRAM-MD5

[Sathya Sundaresan]

Attaching the modified Smtp.cs and the MD5 Keyed
Hashing Algorithm implementation class from MSDN that
I have used.

Please consider updating version with this feature.
Thanks.

[Sathya Sundaresan]

Zip file with Smtp.cs and HMACMD5.cs

[Ian Stallings]

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Thanks, I will add this to the next release.