We support HTML, and you can add your own HTML tag from the Code view in your Sequence section.
HTML formatting will be removed if you have these settings enabled:
Delivery Optimization
Go to campaign's Options section
Look for "Delivery Optimization"
Send emails as text-only(no HTML): When enabled, this sends all emails as plain text, and HTML format will be removed for all steps
Send first email as text-only: When enabled, this sends the first email as plain text, and the HTML format will be removed for Step 1
Advanced Deliverability Settings
Always send first email as text-only: Removes HTML from Step 1 emails across all campaigns
For best deliverability, plain text emails perform better than HTML emails. We strongly encourage you not to use too much HTML or media, especially not in your initial email.