# How to avoid Outlook's spam folder > Outlook and Microsoft 365 weight sender reputation heavily and run aggressive link/attachment scanners. Authenticate, build reputation slowly, and keep complaints near zero. Microsoft (Outlook.com, Hotmail, Live, and Microsoft 365 / Exchange Online) is often the toughest mailbox provider for new senders. It leans hard on **sender reputation** and tends to react sharply to sudden volume or any complaint signal — sometimes routing mail to **Junk** with little warning. The fundamentals are the same as Gmail — authenticate, warm up, keep complaints low — but a few Microsoft-specific points matter. ## Authenticate, including DMARC Publish **SPF, DKIM, and DMARC**. Microsoft checks all three and uses DMARC alignment as a trust signal. Authentication is **required** for bulk senders (roughly **5,000+ messages per day**) and strongly recommended for everyone else. MailBlastr generates SPF and DKIM when you verify a domain; you add the DMARC record. See [DNS records](https://www.mailblastr.com/docs/domains/dns). Set a recognizable sender name on your `from` (for example `Acme Updates `) rather than a bare address — Microsoft surfaces and weighs the display name. ## Reputation is everything — warm up slowly Microsoft has no public reputation dashboard like Gmail's Postmaster Tools (its **SNDS** covers IPs, which on MailBlastr's shared IP pool you don't control), so you can't inspect your standing as easily. That makes a careful [warm-up](https://www.mailblastr.com/docs/kb/warm-up) even more important: start small, grow volume in steps, and prioritize your **most engaged** recipients first so early Microsoft signals are positive. > **Warning:** Microsoft is quick to throttle. If you see SMTP responses mentioning a high spam complaint rate or unusual sending pattern, slow down immediately — pushing through makes it worse. ## Keep complaints near zero Microsoft runs a **Junk Mail Reporting Program (JMRP)** feedback loop. On MailBlastr's shared IP pool you generally can't enroll your own IP, so your best defense is preventing complaints in the first place: mail only people who opted in, make unsubscribe obvious, and remove anyone who disengages. MailBlastr auto-suppresses complaints account-wide — see [the suppression list](https://www.mailblastr.com/docs/kb/suppression-list). ## Don't be alarmed by 'phantom' opens and clicks Microsoft Defender / ATP **Safe Links** and **Safe Attachments**, plus gateways like Mimecast and Proofpoint, fetch every image and follow every link at delivery time — before a human sees the message. MailBlastr filters these scanner user-agents out of your open and click counts, so your engagement numbers stay honest. If your Microsoft open rate looks low, it is usually real, not a tracking artifact. ## Build positive engagement signals A few low-effort actions create the early positive signals Microsoft looks for, especially when you're getting started: - **Engage with your own mail.** Send a message to yourself on Outlook.com, open it, and reply — that interaction is a genuine positive signal. - **Add yourself, and ask recipients to add you, as a contact / Safe Sender.** Mail from known contacts skips much of the junk filtering. - **Don't blast a single message to a big BCC list.** Send individual messages (which is what MailBlastr does per recipient) rather than one mail BCC'd to hundreds — bulk BCC is a strong spam tell to Microsoft. - **Keep the spam-complaint rate under 0.3%.** Stop sending to a stream that shows no engagement, and never keep mailing an address that unsubscribed or is bouncing. ## Content tips that matter to Microsoft - Keep HTML clean and well-formed, and as **close to plain text** as you reasonably can; broken or bloated HTML scores poorly with Microsoft's filters. - Avoid large image-only emails, risky attachment types, and URL shorteners. - Use a consistent, monitored `From` address and a real `Reply-To`. - Maintain steady volume — gaps followed by bursts read as suspicious.