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Original research

The Email Deliverability Index

Email hosting reviews talk about storage and price. The question that matters is whether your mail lands in the inbox. Once a month we send the same message from every email host we cover, exactly as a new customer would be set up, to real inboxes at the four largest consumer mail providers — and record where it landed and what the receiver's authentication checks said.

Methodology published · First run pending

Method

  1. One mailbox per host, default setup. Each email provider in our directory gets a paid mailbox on its own subdomain of a domain we control, configured exactly as the provider's own onboarding instructs — its SPF include, its DKIM keys, its recommended DMARC policy. We do not add third-party relays or tune anything the vendor didn't tell us to.
  2. Identical message, identical moment. On the first of each month, a plain-text message with the same body and a subject carrying the run identifier is sent from every host to every seed inbox within the same hour.
  3. Real receivers. Seed inboxes at Gmail, Outlook.com, Yahoo Mail, and iCloud, plus a mailbox on a domain we run with DMARC reporting enabled. Consumer inboxes, not enterprise tenants with custom filtering.
  4. Placement read two to four hours later. Each seed inbox is read over IMAP and every test message is classified: inbox, promotions tab, spam, or missing. Bounces are recorded as bounced.
  5. Authentication from the receiver's headers. SPF, DKIM, and DMARC results are taken from the receiving provider's Authentication-Results header — what Gmail or Outlook actually concluded, not what the sender's dashboard claims.

Why subdomains, and what this can't tell you

Separate subdomains keep one provider's sending reputation from leaking onto another's. The trade-off is that every sender starts with a young domain and no history — which is also exactly the situation a new customer is in. Results measure the provider's shared infrastructure and defaults, not what a mature domain with years of clean sending could achieve. A "spam" result does not mean your mail will be spam; it means a brand-new customer's first mail on that host landed there this month.

Results

No runs have been recorded yet. The first monthly run follows mailbox setup on each provider; the roster and mailbox purchase dates will be published here first.

Open data: deliverability.json · See all datasets and methodology · Email hosts we cover: Best Email Hosting.