How to Block a Sender and Stop Spam Reaching a Business Mailbox

Blocking a sender is satisfying and mostly useless against real spam, because the next message comes from a different address. It does work for the persistent salesperson or the ex-supplier who will not stop. This guide covers how to block in each app, what to do instead for bulk spam, and the two mailbox habits that reduce junk more than any button.

Quick answer

Use Block for a specific person or company that keeps writing from the same address. For random spam, use Report spam or Mark as junk instead; it trains the filter on patterns rather than one address, and it moves future look-alikes automatically. Never reply to spam, even to say stop, and never click an unsubscribe link in a message you did not sign up for.

How to block in each app

• Webmail on a business host: open the message, use the menu (three dots) and choose Block sender, or create a rule: From ends with @annoying-vendor.com, move to Trash or Junk. Server rules apply on every device.
• Outlook desktop: right-click the message, Junk, Block Sender. Manage the list under Junk E-mail Options, Blocked Senders. You can block a whole domain such as @vendor.com or even a top-level domain.
• Outlook.com / new Outlook: Settings, Mail, Junk email, Blocked senders and domains.
• Apple Mail: click the sender name in the header and choose Block Contact. Under Mail, Settings, Junk Mail, Blocked, choose whether blocked mail goes to Trash or stays in Inbox with a marker.
• Gmail: open the message, three dots, Block. Blocked mail goes to Spam.
• iOS Mail: tap the sender, then Block this Contact. Blocked messages are marked or moved depending on Settings, Mail, Blocked Sender Options.

What to do about real spam

1. Mark it as spam or junk rather than deleting it. Each report improves the filter for that mailbox.
2. Do not open images or click links; opening a tracking pixel confirms your address is live.
3. Check whether the spam is arriving at a catch-all or an old alias. Retiring an address that only receives junk removes the problem entirely.
4. If the spam is addressed to a role mailbox published on your website, replace the plain address on the site with a contact form or an obfuscated address, and keep the real one for replies.
5. Look at the authentication (proof that email really comes from your company)-Results header. Spam that fails SPF or DKIM would be caught by a stricter setting if your host offers one.

Two habits that cut spam more than blocking

• Separate public and private addresses. Publish hello@ and support@; keep personal addresses for people you have actually corresponded with. When a public address becomes unusable, retire and replace it without disrupting anyone's personal mail.
• Publish DMARC. A p=quarantine or p=reject policy stops spammers from forging your own domain in mail to you and your customers. OquMail guides you through SPF, DKIM and DMARC with live verification when you add your domain, and the starting DMARC record it gives you is v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com.

When to block a legitimate sender

Sometimes the nuisance is not spam but a real business that ignores requests to stop: a recruiter, a marketing agency, a former vendor. Blocking their domain is reasonable after you have asked once in writing. Keep the request in your Sent folder in case they later claim you never told them; in many jurisdictions unsolicited business email after an explicit opt-out is a regulatory matter, not just a nuisance.

Pitfalls

• Blocking a whole free-mail domain. Blocking @gmail.com to stop one spammer also blocks every customer on Gmail.
• Blocking on one device only. A block in Apple Mail on your Mac does nothing for your phone or webmail. Use a server-side rule where possible.
• Auto-deleting blocked mail. Move it to Junk instead so a mistaken block can be undone.
• Assuming the From address is real. Spam often spoofs a known contact; blocking that contact then blocks the real person. Report as spam instead of blocking.

Common questions

Does the blocked sender know they are blocked?

No. Blocked mail is accepted and then filed or discarded silently. Their message does not bounce, and nothing is sent back to them.

Why is spam still arriving after I blocked it?

Because the next message came from a different address, which is how bulk spam works. Use Report spam so the filter learns the pattern, and check that the block was created server-side rather than in a single app.

Can I block an entire country or language?

Outlook desktop can block top-level domains and character sets under Junk E-mail Options, International. It is blunt; you will also block legitimate senders from those regions. Use it only if you genuinely never do business there.