devise

https://github.com/plataformatec/devise

Ruby

Flexible authentication solution for Rails with Warden.

Mail.register_observer

You can register an object to be informed of every email that is sent through
this method.

Your object needs to respond to a single method #delivered_email(mail)
which receives the email that is sent.

Source | Google | Stack overflow

Edit

git clone [email protected]:plataformatec/devise.git
cd devise
open

Contribute

# Make a new branch

git checkout -b -your-name--update-docs-Mail-register_observer-for-pr

# Commit to git

git add git commit -m "better docs for Mail.register_observer"

# Open pull request

gem install hub # on a mac you can `brew install hub`

hub fork

git push <your name> -your-name--update-docs-Mail-register_observer-for-pr

hub pull-request

# Celebrate!