Action Mailer is framework for designing email-service layers. These layers
are used to consolidate code for sending out forgotten passwords, welcoming
wishes on signup, invoices for billing, and any other use case that requires
a written notification to either a person or another system.

Additionally, an Action Mailer class can be used to process incoming email,
such as allowing a weblog to accept new posts from an email (which could even
have been sent from a phone)

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