[FEATURE] Add support for SMTP email server

[yerikvaliyev]

Feature Description

Add support for sending emails with a custom SMTP server. (Currently only AWS SES is supported)

Possible Implementation

Could be implemented using lettre crate.
Steps to implement:

• Create the email building and sending logic
• Impl the EmailClient trait
• Add a new arm to the match statement in create_email_client() function

Have you spent some time checking if this feature request has been raised before?

• I checked and didn't find a similar issue

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

Are you willing to submit a PR?

Yes, I am willing to submit a PR!