v2.8.1

Correct encryption types SSL/TLS and STARTTLS

Previously EncryptionTLS correspond to STARTTLS and EncryptionSSL correspond to SSL/TLS.

To avoid confusion in names, two new const were created:

• EncryptionSTARTTLS for STARTTLS
• EncryptionSSLTLS for SSL/TLS

EncryptionTLS and EncryptionSSL are deprecated and will be removed in future.

Also, thanks for this contributors for these changes:

@simaotwx

• Fix typo in error message 8dcac4e

@simonerota

• Properly detect mime type when attaching using base64 c1a7db7