This update modernizes the mass mailing email design experience by moving it to the newer website-style editor, refreshing templates, and improving how layouts behave across screen sizes. It also cleans up messaging internals and adds limited support for sending notification emails to addresses that are not linked to contacts, helping support cases such as out-of-office replies without creating extra records.

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




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