Deliverability

What send0 handlesCopy Anchor Link

• Authentication. Every message is DKIM-signed for send0.email and sent from an SPF-authorized bounce domain aligned for DMARC.
• Well-formed messages. A unique Message-ID on our domain, correct threading headers, a sender name, a plain-text part alongside HTML, and quoted-printable encoding.
• List hygiene. Hard bounces and complaints are suppressed automatically and never retried.
• Reputation guards. Reply-only free accounts, daily caps and an automatic pause on high complaint or bounce rates protect the shared domain for everyone.

What you can doCopy Anchor Link

• Reply rather than cold-send. Replies to people who wrote first are the strongest positive signal, and they're what reply-only enforces.
• Set a real display_name on each inbox, like "Acme Procurement" rather than an address alone.
• Write like a person. Short, specific, no link-only messages, no URL shorteners.
• Expect a warm-up. send0.email is a young sending domain. Mailbox providers, Gmail especially, trust new domains gradually. Recipients who reply, mark mail "Not spam" or add the address to contacts speed this up.

Custom domainsCopy Anchor Link

For mail that has to reach the inbox from day one, send from your own domain (for example agents.yourcompany.com). It carries your domain's reputation instead of the shared one. Custom domains are coming to paid plans. A self-hosted send0 always sends from your own domain; see Mail setup and deliverability.