How to improve newsletter deliverability on Microsoft 365

Deliverability is whether your newsletter reaches the inbox rather than the spam folder. On Microsoft 365, most of it comes down to proving you are a legitimate sender and keeping your list clean. Use this checklist.

Deliverability checklist

1. Authenticate your domain. Configure SPF, DKIM, and DMARC for every domain you send from, and work DMARC up to p=reject. See our SPF, DKIM, and DMARC guide.
2. Send from your own domain and mailbox. Sending from the address recipients already trust beats a shared marketing IP. This is the core of how SimpleNewsletter365 works.
3. Keep your list clean. Remove hard bounces and long-inactive addresses, and never email purchased or scraped lists. High bounce and complaint rates hurt your reputation quickly.
4. Make unsubscribing easy. A clear, working unsubscribe reduces spam complaints, which are one of the strongest negative signals.
5. Respect sending limits and pace. Microsoft 365 caps sending per mailbox and per tenant. Pacing large sends keeps you within Microsoft 365 sending limits and looks natural to inbox providers.
6. Warm up gradually. Ramp volume on newer domains by starting with your most engaged recipients.
7. Monitor results. Watch delivered, bounced, and unsubscribed for every send, and investigate sudden changes.

Why the sending path matters

Many newsletter tools send from a shared marketing IP and domain. If that shared pool has senders with poor reputation, your mail can suffer for it. SimpleNewsletter365 sends each newsletter through your own Microsoft 365 mailbox over Microsoft Graph, so your deliverability rests on your own domain’s reputation, not a pool you do not control.

Related guides

• SPF, DKIM, and DMARC for Microsoft 365 senders
• Microsoft 365 email sending limits explained
• How to send a newsletter from Microsoft 365

Sources

• Email authentication in cloud organizations (Microsoft Learn)
• Microsoft 365 outbound sending limits (Microsoft Learn)

Frequently asked questions

Why do my Microsoft 365 newsletters go to spam?

The most common causes are missing email authentication (SPF, DKIM, DMARC), sending from a shared marketing IP that recipients do not recognize, poor list hygiene with old or invalid addresses, and no clear unsubscribe. Fixing authentication and sending from your own domain usually helps the most.

Does sending from my own Microsoft 365 mailbox improve deliverability?

Generally yes. Sending from your own mailbox and domain uses the sender reputation your organization already has, rather than a shared marketing IP used by many senders, so recipients and inbox providers are more likely to trust it.

How do I warm up sending on a new domain?

Start with smaller, engaged segments and increase volume gradually so inbox providers see a steady, wanted sending pattern. SimpleNewsletter365 paces sends within Microsoft 365 limits, which supports a steady ramp.