fixed smtp starttls issue

[aman566]

Fixed #327 starttls issue by using ehlo command to check wheather IP supports tls connection or not.

Checklist

• I have followed the Contributor Guidelines.
• The code has been thoroughly tested in my local development environment with flake8 and pylint.
• The code is both Python 2 and Python 3 compatible.
• The code follows the PEP8 styling guidelines with 4 spaces indentation.
• This Pull Request relates to only one issue or only one feature
• I have referenced the coresspoinding issue number in my commit message
• I have added the relevant documentation.
• My branch is up-to-date with the Upstream master branch.

Your development environment

• OS: Linux
• OS Version: Ubuntu 18.04
• Python Version: 3.8