Allow set SMTP_PORT on config

[caiquecastro]

Proposed changes

It assumes the port is 2525, but if I have a local server for development and a production SMTP server with different ports, it's needed to be configurable

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

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• I have read the CONTRIBUTING doc
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

Further comments

N/A

[coveralls]

Coverage decreased (-8.9%) to 84.211% when pulling 32cf6e2 on caiquecastro:patch-1 into 4aef9bb on adonisjs:develop.