Why are my emails going to spam?

How receivers decide

There is no single spam score you can look up. Gmail, Outlook.com, Yahoo and every corporate mail filter weigh dozens of signals, most of which fall into four groups: authentication (can the receiver prove the mail really comes from your domain?), infrastructure (does the sending server look like a properly run mail server?), reputation (how have recipients reacted to your mail in the past?) and content. Work through them in that order - content tweaks don't help while authentication fails.

1. Authentication: SPF, DKIM and DMARC

Unauthenticated mail is the most common cause, and the easiest to fix. Check that your domain has:

• One valid SPF record listing every service that sends as your domain, within the 10-lookup limit.
• A DKIM signature with your own domain in d=, ideally a 2048-bit key.
• A DMARC record, and mail whose From: domain aligns with SPF or DKIM.

The quickest test: send a message to a Gmail or Outlook.com address, open "Show original" (or "View message source") and read the Authentication-Results header. You want to see:

spf=pass smtp.mailfrom=example.com;
dkim=pass header.d=example.com;
dmarc=pass header.from=example.com

You can also look up all your records at once with the email authentication checker.

2. Infrastructure: reverse DNS and TLS

Receivers expect the sending server's IP address to have a PTR record (reverse DNS) whose hostname resolves back to the same IP - "forward-confirmed reverse DNS". A server without it looks like an infected home computer, and Gmail rejects or spam-folders such mail. Reverse DNS is set by whoever owns the IP address (your hosting or cloud provider), not in your domain's DNS zone - so if you run your own mail server, ask your provider to set it. With a hosted service it is the provider's job; with AnyMail, it is ours and there is nothing to configure in your domain.

Mail should also travel over an encrypted (TLS) connection. Gmail shows a red open-lock icon on messages it received unencrypted, and requires TLS from bulk senders.

3. Reputation: volume, complaints and warm-up

New domains and IP addresses

A domain or IP address with no history has no reputation, and receivers are cautious with strangers. Sending thousands of messages from a brand-new domain on day one is exactly what spammers do. Start with normal, person-to-person volume and increase gradually over a few weeks ("warm-up"). AnyMail enforces this on its side: each mail server starts with a lower hourly sending cap that rises over its first two weeks, which protects your reputation and that of the shared sending IP.

Spam complaints

Every "Report spam" click counts against you. Google asks senders to keep the complaint rate reported in Postmaster Tools below 0.3%, and well below 0.1% to be safe. The causes are almost always the same: mail people didn't ask for, mail they no longer want, and no easy way to stop it.

List hygiene

• Send only to people who opted in, and never to purchased or scraped lists.
• Remove addresses that bounce; repeated sending to non-existent mailboxes is a strong spam signal.
• Stop mailing people who haven't opened anything for months.
• Check whether your domain or IP appears on public blocklists such as Spamhaus; a listing usually points to a compromised account or a bad list.

4. Content and formatting

• Write like a person: a clear subject line, no ALL CAPS, no piles of exclamation marks, no "100% free" promises.
• Avoid image-only messages; include a real text part and keep the HTML simple and valid.
• Use links on your own domain. URL shorteners and links whose visible text shows a different domain than the real target are classic phishing signs.
• Be careful with attachments, especially archives and documents with macros; link to a file instead.
• Keep the From: address consistent and make sure Reply-To and the sender name match who you are.

Unsubscribing: List-Unsubscribe

For newsletters and other mail people subscribed to, add a List-Unsubscribe header so mail apps can show their own "Unsubscribe" button - and honor it promptly. Gmail and Yahoo require bulk senders to support one-click unsubscribe (RFC 8058) and to process requests within two days. People who can unsubscribe easily don't press "Report spam" instead. AnyMail adds a one-click List-Unsubscribe header to every message it delivers to an external recipient and stops delivering to recipients who have unsubscribed from that mail server.

The Gmail and Yahoo sender requirements (2024)

In February 2024 Google and Yahoo started enforcing new rules. Every sender is expected to:

• authenticate mail with SPF or DKIM,
• send from IPs with valid forward and reverse DNS,
• use TLS, follow the message format standard (RFC 5322) and keep spam complaints low.

Bulk senders - Google's threshold is around 5,000 messages a day to Gmail addresses - must additionally publish SPF and DKIM, a DMARC record (at least p=none), have their From: domain aligned with SPF or DKIM, and offer one-click unsubscribe in marketing mail. Microsoft announced similar requirements for high-volume senders to Outlook.com in 2025. The exact thresholds and enforcement details change over time, so check each provider's current sender guidelines - but a domain that meets the list above is in good shape everywhere.

A quick checklist

1. SPF, DKIM and DMARC all pass and align (read the headers of a test message).
2. The sending server has forward-confirmed reverse DNS and uses TLS.
3. Volume on a new domain grows gradually.
4. Recipients opted in, bounces are removed, and unsubscribing takes one click.
5. The content reads like something the recipient expects.
6. For domains sending to Gmail regularly, register in Google Postmaster Tools to watch reputation and complaint rates.

AnyMail takes care of the parts on the server side - DKIM signing, the records to publish and automatic checks of them, reverse DNS of the sending IP, one-click unsubscribe and gradual warm-up - so you can focus on sending mail people want.