MailSlurp guide agent setup

Title: HTML email signatures in Outlook, Gmail and Apple Mail: what changes (tested 2026)
Description: Why HTML email signatures look different in Outlook, Gmail and dark mode. Three signature styles rendered on 12 email apps, with screenshots.
Canonical URL: https://www.mailslurp.com/guides/email-client-support/email-signatures/
Markdown URL: https://www.mailslurp.com/guides/email-client-support/email-signatures.md

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.