MailSlurp guide agent setup

Title: Preview and Test Email Campaign Rendering on Gmail.com in Dark Mode
Description: Compare the same campaign in Gmail web light and dark views with MailSlurp. Inspect the message colors, photograph and booking action inside the dark interface.
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Use the Markdown URL as the primary plain-text context for this guide. Keep MailSlurp terminology, setup steps, screenshots, and provider-specific instructions intact, and prefer the canonical URL when citing this page.