Why are my emails suddenly going to spam?

A sudden change usually means your mail server was added to a blacklist, often after a compromised mailbox or abused web form sent spam, or an SPF, DKIM or DMARC record stopped passing after a DNS or provider change.

How do I know if my domain is blacklisted?

Look up your mail server addresses on IP blacklists such as Spamhaus ZEN and SpamCop, and your domain on domain blacklists such as the Spamhaus DBL, SURBL and URIBL. A blacklist check does all of these lookups at once.

How long does it take to get off a blacklist?

Many lists remove a listing automatically once the spam stops, SpamCop within about a day and others within a week. Lists that take removal requests usually act within hours, but only after the cause is fixed.

Can good SPF, DKIM and DMARC records stop my mail going to spam?

They are required, but not enough on their own. A blacklisted server, poor engagement or sending to old lists can still send authenticated mail to spam.

Why Are My Emails Going to Spam? How to Find and Fix It

Your messages leave your outbox, nothing bounces, and recipients still say they never saw them. Inboxes almost never explain why they filtered a message, but when mail from a whole domain or server goes to spam, the cause is usually one of two things you can check from the outside: a blacklisted mail server, or authentication that fails.

First, confirm it's a pattern

Send a test message to a Gmail and an Outlook address you control, and to a colleague at another company. If all of them land in spam, the problem is your server or domain, and the checks below will usually find it. If only one recipient is affected, their own filter rules or a contact-specific block are more likely.

1. Is your mail server on a blacklist?

Blacklists (DNSBLs) are lists of IP addresses and domains seen sending spam. Spam filters query them for every incoming message, and a listing on a major list such as Spamhaus or SpamCop gets mail rejected or quarantined by a large share of business mail servers, often without any bounce to tell you.

The Email Blacklist Check finds your mail servers from your MX records and checks each against IP blacklists, and checks your domain against the domain lists that filter links in messages.

Why servers get listed

A compromised mailbox. A stolen password is used to send spam through your real server. This is the most common cause.
An abused web form. Contact, sign-up and "send to a friend" forms that email arbitrary addresses are a favourite target.
Malware on a server or office machine sending mail directly.
Sending to old or bought lists. Addresses that have been dead for years are turned into spam traps that report every sender.
A shared address. On shared hosting, another customer on the same IP can get it listed.

How to get removed

Stop the source first. Reset passwords and turn on two-factor authentication, add a CAPTCHA to forms, and clean any malware. Lists relist quickly, and some make every repeat removal harder.
Request removal from each list. The check links to every list's lookup and removal page, with the reason the list gives.
Wait for the lists to update. Many expire listings on their own once the spam stops: SpamCop within about a day, others within a week.
Re-run the check to confirm every listing is gone.

A listing on the Spamhaus PBL (Policy Block List) is different: it marks home and dynamic connections that shouldn't send mail directly. It only matters if you run your own mail server on such a connection, and the fix is to send through your provider's servers.

2. Does your mail pass SPF, DKIM and DMARC?

Since 2024, Gmail and Yahoo require bulk senders to authenticate with SPF, DKIM and DMARC, and Outlook followed in 2025. Even for small senders, mail that fails authentication starts with a large penalty. Three records do the work:

SPF lists the servers allowed to send for your domain. Common failures: a sending service missing from the record, two SPF records, or more than 10 DNS lookups.
DKIM signs each message with a key published in your DNS. Common failures: a service that was never set up to sign, or a key that was deleted or rotated.
DMARC tells inboxes what to do when SPF and DKIM don't match your From address. Without it, many providers treat your mail with suspicion.

The Email Authentication Checker reads all three, follows every SPF include and tells you which part fails. Our guide to SPF, DKIM and DMARC explains how they fit together.

3. Does your server's address name itself?

Receiving servers look up the reverse DNS (PTR) of the connecting address. A mail server whose address has no reverse name, or a generic one such as 203-0-113-25.dsl.example.net, looks like a home connection, and many filters treat it as spam. Your hosting or mail provider sets the PTR record; the email checker shows it for each mail server.

What DNS checks can't see

If your server is clean and authentication passes, the remaining causes are about the mail itself and how recipients react to it:

Engagement. Messages that are rarely opened and often marked as spam teach filters to file the next ones there too.
List quality. High bounce rates and spam traps from old addresses damage your sending reputation.
A new domain or server with no history. Start with low volume and increase it gradually.
Content such as link shorteners, links to blacklisted domains, or a message that is a single image.

Gmail's free Postmaster Tools shows how Gmail rates your domain's reputation once you send enough mail.

Keep it from happening again

A blacklisting rarely announces itself: you find out when a customer asks where their invoice went. dnsdon Pro checks every mail and web server against the blacklists each hour, alerts you the moment one is listed, and emails you when SPF, DKIM or DMARC breaks.