What is the “From” header and what does it mean?
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The From header is what you see in your inbox next to an email. It shows the sender's name and email address, like "Captain Kraken <kraken@tidalmail.com>" or "TidalMail Fleet <hello@tidalmail.com>". It has two parts: the display name (the friendly name) and the email address (the technical sender).
This is the header that matters most for DMARC alignment. When an email lands in someone's inbox, the receiving server checks whether the domain in the From header matches the domain that passed SPF or DKIM authentication. If they don't match, DMARC fails. If DMARC fails, your email lands in spam or gets rejected entirely.
Here's why that matters in practice. Let's say you send marketing emails through Mailchimp, and your From header says "newsletter@yourdomain.com". Mailchimp sends the email from their servers, but as long as your SPF or DKIM records are set up correctly and point back to yourdomain.com, DMARC passes. The receiving server sees yourdomain.com in the From header, checks authentication, sees yourdomain.com passed SPF or DKIM, and lets it through.
But if your From header says "newsletter@yourdomain.com" and your authentication points to a different domain (or isn't set up at all), DMARC fails. That's the most common reason marketing emails land in spam even when the content is perfectly fine.
Most ESPs let you customize the From header. You can set both the display name and the email address. The display name is what most people see first ("TidalMail Fleet"), and the email address is what shows when they hover or reply ("hello@tidalmail.com"). You want both to be recognizable and trustworthy.
One mistake: using a no-reply address like "noreply@yourdomain.com". It's not technically wrong, but it tells subscribers you don't want to hear from them. Some inbox providers (especially Gmail) treat this as a negative signal because it discourages engagement. Use a real address that someone monitors, even if it's just to handle unsubscribes or bounce notifications.
If you're using a transactional ESP like Postmark or SendGrid, your From header should match the domain you've authenticated. Most platforms won't let you send from a domain you haven't verified, which is good because it forces you to set up SPF and DKIM correctly. If you're having trouble, check your ESP's documentation for "domain authentication" or "sender authentication".
Want to see how your From header looks to recipients? Send a test email to yourself and check the raw headers with our free Email Header Analyzer. You'll see exactly what domain is in the From field and whether it matches your authenticated domain.
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