How to Send Bulk Email in Outlook (The Right Way in 2026)

Outlook can send bulk email, and Microsoft 365 will take you further than free Outlook.com. But there are limits, there’s a mail-merge route most people don’t know about, and there’s a big authentication change arriving through 2026 that anyone sending via SMTP needs to know about. Here’s how to do it properly.

The Outlook and Microsoft 365 sending limits

What you can send depends on which account you’re on:

• Microsoft 365 (business): up to 10,000 recipients per day, a maximum of 500 recipients per single message, and a rate limit of around 30 messages per minute.
• Free Outlook.com: far lower, in the region of 300 recipients a day, and geared towards personal use.

Those are the technical ceilings. For cold outreach they’re not the number to aim at, because pushing a single mailbox anywhere near a four-figure daily volume is a reliable way to damage its reputation.

The 2026 authentication change you need to know

If you send from Outlook through an app or an SMTP client, this matters. Microsoft is phasing out basic authentication (a plain username and password) for SMTP submission. Through 2026 it moves to being disabled by default, and new Microsoft 365 tenants won’t have it available. The replacement is OAuth 2.0, a token-based sign-in that most modern sending tools support natively.

Option 1: mail merge with Word and Outlook

For personalised bulk email to a list, Word’s mail merge feeding into Outlook is the built-in route:

1. Put your contacts in an Excel spreadsheet, one row per person, with columns for name, email and any merge fields.
2. In Word, go to Mailings, then Start Mail Merge, and choose E-mail Messages.
3. Select your spreadsheet as the recipient list and insert merge fields where you want personalisation.
4. Finish and merge to email, and Word sends each personalised copy through Outlook.

It works, and each recipient gets their own message rather than a giant CC list. But it sends everything through your one Outlook account, so you’re bound by that mailbox’s daily limit, and there are no follow-ups and no warmup behind it.

Option 2: don’t use BCC

The tempting shortcut is one email with a hundred people in BCC. Don’t. Everyone gets the same unpersonalised message, there’s no unsubscribe handling, and large BCC sends are a well-known spam signal. It’s the fastest way to end up filtered.

Why one Outlook account isn’t enough for cold email

The same three gaps that limit Gmail limit Outlook for serious outbound:

1. Sending is concentrated on one mailbox. High cold volume from a single address damages its reputation quickly.
2. No warmup. Mailboxes need to build a sending reputation gradually. Outlook has no built-in way to do this.
3. No campaign machinery. Follow-ups, reply handling and sending across several inboxes are a lot to run by hand.

Doing it properly with rotation and warmup

Dedicated cold email software solves this, and HotHawk connects Microsoft inboxes over OAuth so it’s ready for the 2026 auth change out of the box. You connect several mailboxes, warm them up on real Google and Microsoft inboxes, and let inbox rotation spread your sending across all of them so no single mailbox carries too much. Your total daily reach climbs while each individual inbox stays healthy.

A cold email sequencer runs the campaign itself, personalised first email, follow-ups that stop when someone replies, and every response in one Master Inbox. You’re still sending through Microsoft, you’re just doing it the way that holds up at volume.

A few common questions

How many emails can I send from Outlook per day? Microsoft 365 business accounts allow up to 10,000 recipients a day, with 500 recipients per message and around 30 messages a minute. Free Outlook.com is far lower, roughly 300 recipients a day.

Is Microsoft turning off basic authentication for Outlook SMTP? Yes. Through 2026 Microsoft is retiring basic authentication for SMTP submission, moving to disabled-by-default with OAuth 2.0 as the replacement. Sending tools that connect over OAuth keep working. Check Microsoft’s current documentation for exact dates.

Can I send bulk cold email from a single Outlook account? Only a little. Concentrating high cold volume on one mailbox damages its reputation fast. Serious outbound spreads a modest daily volume across several warmed-up inboxes.

Does Outlook have a mail merge feature? Yes, via Word. Word’s mail merge, feeding into Outlook, sends personalised copies to a contact list from a spreadsheet. It has no follow-ups or warmup, so it suits small internal campaigns rather than cold outreach.

Setting Outlook up to send through an app? You’ll want the Outlook SMTP settings. Sending from Google instead? The how to send mass email in Gmail guide covers the same ground for Gmail and Google Workspace.