Why are my emails going to spam? The causes and the order to fix them

Why are my emails going to spam? The short answer

Emails go to spam when authentication fails, when recipients mark them as spam, when a new domain sends too much too soon or when the list is poor. Check the causes in that order. Warmy's help center says low deliverability is almost never caused by one thing. Rules below were read on October 23, 2026.

To see which cause applies, every Warmy plan, from $49 a month, includes a deliverability tester that checks placement, authentication and blacklists, and a DMARC tracker. Best inbox placement tools compares it with other testers.

Cause 1: SPF, DKIM or DMARC fails

SPF, DKIM and DMARC are DNS checks of who may send as your domain. Google requires SPF or DKIM from every sender to Gmail, and all three from bulk senders, meaning close to 5,000 or more messages a day to personal Gmail accounts; unauthenticated mail might be marked as spam or rejected with a 5.7.26 error. Yahoo asks bulk senders for SPF, DKIM and a DMARC policy of at least p=none, and sets no volume threshold.

Outlook.com, Microsoft's consumer service, asks domains sending over 5,000 emails a day for SPF, DKIM and DMARC at p=none or stricter. Its pages say non-compliant mail goes to Junk and may be rejected, with no date given. Warmy's calculator page says warm-up emails will not get through if these records fail, so start with how to set up SPF, DKIM and DMARC.

Cause 2: recipients mark your mail as spam

The spam rate is the share of your messages that recipients mark as spam in Gmail, shown in Google Postmaster Tools. Google's FAQ says to keep it below 0.1% and prevent it from ever reaching 0.3% or higher; bulk senders become eligible for mitigation after 7 consecutive days below 0.3%.

Yahoo also says to stay below 0.3%, and that poor reputation plus high complaints can send mail to spam. Microsoft calls the junk-complaint rate a principal factor in reputation at Outlook.com.

Cause 3: a new domain sends too much too soon

Google says raising your sending volume too quickly can cause delivery issues, and calls a domain new if it has not sent more than 5,000 emails a day to personal Gmail accounts since January 1, 2024. It advises a low starting volume to engaged users, raised slowly, and its guidelines give no warm-up schedule. Yahoo says a sudden spike can get a sender flagged as compromised.

Warmy's help center claims Outlook is cautious with new domains, and advises against using your primary domain for cold outreach.

Cause 4: the list and the content

Google says not to purchase email addresses from other companies, and Yahoo says not to purchase mailing lists. Microsoft advises removing invalid addresses regularly, and its Outlook.com filters weigh list accuracy, complaint rates and content. Verifying the list is a separate job.

How to find which cause applies

1. Run a placement test. Warmy's checker lists Gmail, Outlook, Yahoo and Zoho as B2C providers and Google Workspace, MS 365 and SMTP as B2B providers.
2. Read your DMARC reports. Warmy's tracker needs a rua tag in your DMARC record, and its first reports arrive within one to two days.
3. Open Postmaster Tools for Gmail. It covers personal Gmail accounts only and may show no data on low-volume days.
4. Fix the earliest cause, then test again; Google says Gmail needs time to adjust after your spam rate improves.

A sender whose records fail needs no paid tool; fixing DNS records costs nothing. A sender under 20 cold emails a day per inbox may need no warm-up, per MailReach's blog, a warm-up vendor's view. Move to a tool when records pass and mail still lands in spam: GlockApps lists a free plan with 2 spam test credits a month.

A 7-day Warmy trial on one mailbox includes a deliverability test that shows the folder your mail reaches; the Terms convert the trial to a paid plan unless you cancel first. Gmail bulk sender requirements lists each provider's rules.