Why are my emails going to spam all of a sudden?

If your emails have suddenly started landing in spam, or bouncing back as blocked, the cause is almost always one of three things: your email isn't properly authenticated, you've sent a lot more than usual, or too many people have marked it as spam. Gmail and Outlook have tightened their rules over the last two years, so something that worked last year can stop working now.

What Gmail requires

Since February 2024, Gmail has asked everyone who sends to Gmail addresses to:

• set up SPF or DKIM, the records that prove an email really came from your domain;
• have valid DNS records for the sending servers and use a secure connection;
• keep the spam rate below 0.3%. Google recommends staying under 0.1%.

Bulk senders, meaning anyone who has sent 5,000 or more messages to personal Gmail accounts in a day, even once, must also have SPF, DKIM and DMARC, and their marketing emails need a one-click unsubscribe and a visible unsubscribe link. Google recommends acting on unsubscribe requests within 48 hours.

Google says that from November 2025 it has been "ramping up its enforcement". Mail that doesn't meet the rules can be temporarily or permanently rejected.

What Outlook and Yahoo require

Microsoft requires SPF, DKIM and DMARC from domains sending more than 5,000 emails a day to Outlook.com addresses. Since May 2025 it rejects mail that doesn't pass. It also says smaller senders benefit from the same setup. Yahoo's rules are much the same as Gmail's, and it asks bulk senders to honour unsubscribes within two days.

The usual causes, and the fixes

1. Authentication isn't set up, or it's broken. This is the most common one, and it often breaks without anyone noticing when a business adds a new tool that sends email on its behalf, like a CRM, a quoting tool or a newsletter service. Check that SPF, DKIM and DMARC are all in place for your domain, and that every service sending as you is included. Your IT provider or your Google Workspace or Microsoft 365 admin can check it in a few minutes.

2. A sudden jump in volume. Google is specific about this. It says to avoid sudden volume spikes if you don't have a history of sending large volumes, and that "immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops". An inbox that normally sends twenty emails a day and then sends a few hundred will look like spam to Gmail, whatever's in it. Start small and build up slowly, and if messages start bouncing, Google's advice is to send less.

3. Too many complaints. Every time someone clicks "Report spam", it counts against you. Cold email and stale lists cause the most. Only email people who'd expect to hear from you, take bounced addresses off your list and make unsubscribing easy, because someone who can't find the unsubscribe link reports you as spam instead.

4. No unsubscribe on marketing email. Gmail wants a one-click unsubscribe on marketing messages, and in Australia the Spam Act requires a working unsubscribe anyway. I've covered the legal side in is cold email legal in Australia?.

Keep your everyday email safe

In my view, the email your business runs on, like quotes, invoices and replies to customers, shouldn't share a reputation with marketing or cold email. If a campaign goes wrong, you don't want your quotes going to spam with it. Sending marketing from a separate domain or subdomain, set up properly, keeps the two apart.

If you'd like your follow-up emails sent at a sensible pace, with unsubscribes handled for you, that's part of our CRM and follow-up work.

How we help with this: CRM and follow-up →