The following modules assist with managing emails and messages. There is the start of an email newsletter comparison at Comparison of email newsletter oriented modules.

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jimcaruso’s picture

jimcaruso commented

These are modules that support the recent transactional email service offerings.

These first few are branded offerings with free and chargeable levels:
Mandrill (from MailChimp)
Amazon SES (Simple Email Service) from AWS (Amazon Web Services)
SendGrid Integration

These support any or multiple SMTP (Simple Mail Transfer Protocol) email services.
Very many Email Service Providers (ESP) offer various SMTP interfaces to their service.

SMTP Authentication Support