Your Message Has Been Blocked in Gmail: Causes and Fixes

"Your message has been blocked" means the receiving server refused your email while it was being delivered, so it never reached the inbox or the spam folder. The reason is in the line that starts "The response from the remote server was." Read that line, match it to the table below, and fix that one thing before you resend anything.

Most advice on this error says "set up SPF, DKIM and DMARC and check your IP reputation." The first half is right, often. The second half is wrong for anyone sending from Gmail or Google Workspace: your mail leaves from Google's servers, so the IP address isn't yours to improve. What's judged is your domain, your authentication and your behavior.

What the bounce is telling you

You received a message from "Mail Delivery Subsystem" with a heading like "Message blocked" and the line "Your message to name@company.com has been blocked. See technical details below for more information." Below it is a code (a 5xx number plus a dotted code such as 5.7.1) and a sentence from the other server. A code that starts with 5 is a permanent refusal for that message. A code that starts with 4 means the server asked you to try again later. Sending the identical message to the same address again will, in most cases, get the identical refusal.

Match the wording to the cause

The codes and their wording come from Google's own SMTP error reference. If your bounce has a different code, search that exact code on the page the bounce links to; each has its own entry.

Cause 1: failed authentication

This is the most common one for someone on a new custom domain. Test it in two minutes. Send a message from the address that bounced to a free Gmail account you own. Open it, click the three dots and choose Show original. At the top you'll see three lines: SPF, DKIM and DMARC, each marked PASS or FAIL. Any FAIL is your fix. Our SPF, DKIM and DMARC guide has the records, and DMARC fail: what it means and how to fix it goes through the order of repairs.

Cause 2: a sudden jump in volume

Imre sells commercial awning installations. He registered a new domain, set it up on a Tuesday, and sent 90 cold emails the same afternoon. Thirty-one came back blocked with a 5.7.1 "likely unsolicited" line. Nothing in his wording was wrong. A domain with no history that goes from zero to 90 in one afternoon looks like the opening move of a spam run. The fix was to stop, wait a day, and send 10 the next morning, then 15, then 20. The ramp in warming up a Gmail account is the model.

Cause 3: links and content

Filters look at the links in a message: shortened links, many different domains, links to brand-new sites, and click-tracking redirects that send every link through a third party. Remove link shorteners entirely. Send your first email with no link, or one link to your own site. If you use a tool that tracks clicks, turn click tracking off for cold sends and see if the blocks stop. The case for plainer emails is in HTML versus plain text.

Cause 4: the recipient's own rules

Sometimes the block has nothing to do with you. A company's mail administrator can refuse mail from outside senders, from new domains, or from a whole category. If your emails to one company bounce and everyone else's go through, this is the likely reason. You can't fix it from your side. Reach that person another way, or ask someone who knows them to pass your note along. If a whole batch of addresses at different companies are all blocked, it's yours.

One company or everyone: count the blocks

Before you change anything, line up the last batch against the bounces. Make three columns: company, did it deliver, what the code said. If every bounce has a different company and the same code, the cause is on your side. If the bounces cluster at two or three companies and the rest went through, the cause is on theirs. If it's a mix, fix your side first, then see what is left. Imre's 31 blocks were spread over 31 companies with the same line, which settled it in a minute.

What Google Postmaster Tools can and can't tell you

Google Postmaster Tools is a free dashboard showing domain reputation and spam rate for mail sent to Gmail users. It's worth adding your domain. But it needs a fair amount of mail to Gmail addresses before it shows anything, so a sender doing 30 a day will mostly see empty charts. Treat a blank dashboard as "not enough volume to say," not as proof that everything is fine. Your Show original check and your bounce codes are the better instruments at this size.

What to change before you resend

1. Fix the single cause the code points to, and only that one.
2. Send a test to your own free Gmail, with Show original open, and confirm three PASS lines.
3. Remove the bounced addresses from the list for now. Don't resend the same text to them the same day.
4. Cut your daily number to half of what it was, and send from the same inbox.
5. Count what comes back after 20 emails. If it's clean, build up. If you still see blocks, pause for a week.

A related but different message is the plain delivery failure, which Gmail message not delivered: read the bounce, fix it covers, and a bounce from a bad list address is covered in cold email bounce rate. For the larger picture of what mailbox providers judge, see the deliverability basics and how to verify email addresses before sending.

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