Customers say your invoices are in their junk folder. Replies to quotes never arrive. Before rewriting your emails, check your domain: most deliverability problems come from missing or broken authentication records, not from the words you use.
1. No SPF record, or a broken one
SPF is a DNS record that lists which servers may send email for your domain. Without it, receiving servers can't tell your real emails from forgeries. Common faults: no record at all, two SPF records (only one is allowed), or a missing service such as your newsletter tool. Build a correct one with the SPF record generator.
2. DKIM isn't switched on
DKIM adds a digital signature to every email so the receiver can check it wasn't changed and really came from your domain. Google Workspace, Microsoft 365, Zoho and most email services provide a DKIM key that you add to your DNS, then switch on in their admin panel. Many businesses add the record but forget the switch.
3. No DMARC policy
DMARC tells receivers what to do with emails that fail SPF and DKIM, and sends you reports. Gmail and Yahoo require a DMARC record from bulk senders, and it helps everyone. Start with p=none to monitor, then move to quarantine and reject. The DMARC record generator builds the record.
4. Your domain or server is on a blacklist
If a server you share (or your own) sent spam, its IP address can land on a blocklist such as Spamhaus. The email deliverability checker looks at the main lists and links you to their removal pages.
5. You send in bulk without meeting the big providers' rules
Since February 2024, Gmail and Yahoo require senders of more than about 5,000 emails a day to authenticate with SPF, DKIM and DMARC, offer one-click unsubscribe, and keep spam complaints under 0.3%. Microsoft (Outlook.com, Hotmail) has applied similar rules to high-volume senders since May 2025. Read the bulk sender rules guide for details.
6. The "From" domain doesn't match the sending domain
Sending as [email protected] through a service that signs with its own domain fails DMARC alignment. In your email or newsletter service, verify your own domain so it signs with your DKIM key.
7. Content and sending habits
- Emails that are a single image with no text, or are full of link shorteners.
- Sudden large sends from a new domain. Increase volume gradually over a few weeks.
- Old, bought or scraped lists, which bring bounces and complaints.
Check your domain in one minute
- Open the email deliverability checker.
- Type your domain (the part after @).
- Fix the items marked in red first, using the exact records the checker suggests, then check again. DNS changes usually show within an hour.
Frequently asked questions
Can I have more than one SPF record?
No. Two SPF records make SPF fail. Merge every service into one record that starts with v=spf1.
Will DMARC p=reject stop my own emails?
It can, if a service you use isn't authenticated yet. That's why you start at p=none, read the reports, fix each sender, and only then tighten the policy.
How long until emails stop going to spam?
Authentication fixes work as soon as DNS updates, usually within an hour. A damaged sender reputation takes days to weeks of clean sending to recover.