Deliverability basics for Microsoft 365 senders

Sending from your own Microsoft 365 mailbox gives you a strong head start on deliverability. Here is a short checklist to keep that advantage.

1. Get your domain authentication right

SPF, DKIM, and DMARC tell inbox providers that mail from your domain is really from you. Microsoft 365 sets up much of this for your domain, but confirm:

• SPF includes Microsoft’s sending hosts for your tenant.
• DKIM signing is enabled for your custom domain in Microsoft 365.
• DMARC is published, ideally moving from p=none to a stricter policy over time as you confirm legitimate sources.

2. Earn consent, then keep it

The fastest way to hurt deliverability is to email people who did not ask. Use double opt-in on your signup forms, only import contacts you have a lawful basis to email, and make unsubscribing easy. We honor unsubscribe state on every send automatically.

3. Watch your bounces and complaints

A spike in bounces or spam complaints is the clearest signal that something is off. Your newsletter reports show delivered, bounced, and unsubscribed counts for every send. Remove addresses that hard bounce, and pay attention to sudden complaint jumps.

4. Respect the pace

Microsoft enforces per-mailbox limits, so very large sends are paced over time. That is a feature, not a bug: steady sending from a trusted mailbox looks far more legitimate than a sudden blast. See sending limits and pacing.

5. Send consistently

Inbox providers reward predictable senders. A regular cadence to an engaged list beats sporadic blasts to a stale one, every time.

Do these five things and your newsletters will land where they should. Start free and send from a domain your recipients already trust.