[done] Third Party Email Providers Poll

The Email feature has not made it into the distributable CodeIgniter 4 yet. The Email class from CI3 did not port gracefully to CI4, and has been redesigned CI4-style. Implementation & testing are under way. This is being developed in the feature/email branch of the CI4 repo.

We held a subforum poll earlier, to see which of the email protocols the community uses, and the answer was all three: mail, sendmail and SMTP.

Planned so far:
[x] separate Email\Email class, which encapsulates an Email entity
[x] Email\TransporterInterface, which abstracts the behavior of a mail transport agent, or a wrapper for same, or even an external email service
[.] Email\Handlers\BaseHandler, which implements the common methods of a Transporter
[.] Email\Handlers\MailHandler, which uses (PHP)mail to send emails; was in CI3
[.] Email\Handlers\SendmailHandler, which uses sendmail to send emails; was in CI3
[.] Email\Handlers\SMTPHandler, which uses SMTP to send emails; was in CI3
[.] revised user guide writeup for handling email
[x] unit testing for Email\Email
[.] unit testing for Email\Handlers\...
[ ] using an external email testing service for unit testing; leaning towads https://mailcatcher.me/


This thread includes a poll, to ascertain the importance of other possible email adapters that might be reasonable to provide.
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This is a roadmap feature, or "epic", and a card on the roadmap board.
Component tasks will show up as issues or PRs on the development board.
We welcome comments & suggestions below.

James Parry
Project Lead