What is a sending domain?

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Your sending domain is the domain shown in the From header of your emails. It's what recipients see when your email lands in their inbox. If you send from newsletter@yourcompany.com, yourcompany.com is your sending domain.

And This matters because mailbox providers use your sending domain to check whether you're who you claim to be. When Gmail, Outlook, or Yahoo receive your email, they check if your SPF, DKIM, and DMARC records line up with the domain in your From header. If they don't align, your emails fail authentication checks and may land in spam or get rejected entirely. Technically, the sending domain is called the Header From domain or RFC5322.From domain. It's different from the return path domain (also called the envelope sender or RFC5821.MailFrom), which is used for bounce handling. Both need to be set up correctly for authentication to work.

Most ESPs handle the technical setup for you. Mailchimp, Brevo, and Klaviyo let you add your domain, then guide you through adding DNS records for authentication. Transactional platforms like Postmark, SendGrid, and Mailgun do the same. The key is using YOUR domain, not theirs (sending from newsletter@yourcompany.com, not newsletter@mailchimp.com).

Want to verify your sending domain is set up correctly? Start with our free SPF checker to make sure your SPF record authorizes your ESP to send on your behalf. Then check your DMARC setup to see if alignment is passing. If something's broken, our SOS hotline is free and we actually pick up ;)

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Yanna-Torry (YT) Aspraki

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I read this on the Email Almanac about sending domains: "Your sending domain is the domain shown in the From header of your emails. It's what recipients see when your email lands in their inbox. Mailbox providers use your sending domain to check whether you're who you claim to be by verifying SPF, DKIM, and DMARC alignment." Help me set up my sending domain correctly. I need: 1. Step-by-step setup for my ESP: what DNS records to add, what values to use, common mistakes 2. Authentication checklist: how to verify SPF, DKIM, and DMARC are all working and aligned 3. Troubleshooting: if my emails are failing authentication or landing in spam, what to check first 4. Best practices: should I use a subdomain (like mail.mycompany.com) or my root domain? What about return path alignment? --- My details (the more you share, the better the advice): - Email platform/ESP: e.g. Mailchimp, SendGrid, Postmark, HubSpot, custom SMTP - Sending domain: the domain you want to send from - Return path domain: if different from sending domain, or "not sure" - Current authentication status: working / partially working / broken / not set up yet - Sending volume: e.g. 5,000/month or 500/day - Email type: marketing newsletters, transactional emails, both - What's not working: describe your current problem or concern

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