How to connect
Outlook, Hotmail & Microsoft 365.
Connect Outlook.com, Hotmail or Microsoft 365 email with Microsoft sign-in. No mailbox password or SMTP server details to paste into MailboxWarm.
Connection preview. You can read this guide and save a mailbox for later. Live authorization and warm-up remain off. Do not enter real credentials while the connection form is disabled.
Before you start
- Access to the Microsoft account that owns the mailbox.
- Permission to authorize an app, or an administrator who can review the request.
Step-by-step setup
Identify the account that hosts your email
Use Microsoft for Outlook.com, Hotmail and Microsoft 365-hosted work email, even when the domain was purchased through another company. Your domain registrar is not necessarily your email provider.
Check organization approval requirements
A managed Microsoft 365 organization may require an administrator’s consent. Ask them to review the requested access when the connection flow is available.
Choose Microsoft in MailboxWarm
Open Mailboxes → Add mailbox, choose Microsoft, and enter your sending email address.
Review and authorize the connection
When connections are enabled, choose Continue with Microsoft. Sign in on Microsoft’s page and review the requested mail permissions. Complete your organization’s approval process if required.
Connection settings
Match these values to the fields in MailboxWarm. Keep passwords and keys private.
- Connection option
- Microsoft
- Authentication
- Microsoft sign-in (OAuth)
- Mail access
- Read/write and send permissions
- SMTP password
- Not required
Check the result
In today’s preview, expect Mailbox saved for later. When connections are enabled, a successful check shows Mailbox connected, with warming still paused. A failed connection check is not proof of delivery or a reason to add the same mailbox again.
Once live warming is available, choose the mailbox’s plan and schedule before starting. Connecting alone does not begin warm-up, and your provider’s sending limits still apply.
Open setup previewTroubleshooting
Administrator approval is required
Send the approval request to your organization’s administrator through Microsoft’s normal process. Do not switch to an SMTP password to bypass consent.
The wrong account opens
Choose the Microsoft account that matches the mailbox address you entered. Return to setup if you selected a different account.
Connection is unavailable
MailboxWarm’s Microsoft authorization readiness is still gated. Saving a mailbox for later does not authorize it.
Provider resources
Provider menus and account policies can change. Use their official documentation for the latest requirements.
Settings reviewed September 12, 2026 · Documentation review, not a live connection test.