[Gwerdonatus]

The installation and multiple-backend guides still lead with EMAIL_BACKEND, although Anymail supports Django 6.1's MAILERS. Document the new configuration, option-name conversion and precedence, and named-mailer routing, while keeping the Django 6.0-and-earlier setup available. Clarify that send_defaults merges with global defaults and webhook settings remain separate.

Addresses the documentation portion of #472; leaves the issue open for any remaining work.

Validation on Python 3.14.7 / Django 6.1.2:

• Full non-live suite: 1,242 tests, OK (5 skipped).
• Sphinx dirhtml build with warnings treated as errors; package README rendering.
• doc8 on both changed pages; git diff --check.
• Executed the documented named-mailer configuration and sending snippets against mocked Mailgun/Postmark responses, verifying provider routing, per-mailer credentials, OPTIONS precedence and the Postmark message stream. No live email was sent.

AI assistance was used to prepare this documentation and its verification; the examples were checked against the implementation and exercised locally.