My email goes to spam at Gmail or Outlook

The same message arriving at one provider and being filed at another is not inconsistency; it is a policy difference. Gmail and Outlook enforce the 2024 sender requirements and evaluate DMARC alignment strictly, where a smaller provider will often deliver an unauthenticated message.

What those two evaluate

Both require an authenticating SPF or DKIM pass aligned with the From domain, a DMARC record on that domain, forward-confirmed reverse DNS on the sending IP, TLS on the connection and a Message-ID header. Miss one and you are not rejected outright, but you start from a reputation deficit that the content then has to overcome.

Above roughly 5,000 messages a day both add one-click unsubscribe (RFC 8058) and a spam complaint rate under 0.3%.

Reputation is per domain and per IP

Both providers score the sending IP and the sending domain separately, over a rolling window. A shared IP at a hosting provider carries whatever its other tenants did; a domain that has never sent to Gmail has no history at all, which is why a first campaign performs worse than the fifth.

This is also why volume spikes hurt: a domain that sends twenty messages a day and then five thousand looks, from the receiver's side, exactly like a compromised account.

Measuring instead of guessing

Gmail's Postmaster Tools shows the domain and IP reputation Google itself computes, plus your complaint rate. DMARC aggregate reports show the same traffic from every reporting receiver, per source, with the SPF and DKIM results after alignment.

Start with the DNS side: the scan at the bottom of this page reports the authentication a receiver will compute for your domain, and a send test measures what happens to one real message, including the PTR and blocklist status of the IP it came from.

Frequently asked questions

It arrives at one customer and not another.

Those customers are on different providers. Gmail and Outlook apply the requirements above; many smaller providers do not, so the same unauthenticated message is delivered by one and filed by the other. The variable is the receiver's policy, not the recipient.

Does having the recipient add me as a contact help?

For that one recipient, yes — a contact entry outweighs a marginal reputation score. It does nothing for anyone else, and it does not change the authentication result, so it is a workaround rather than a fix.