This guide walks you through setting up Microsoft 365 (Outlook) inboxes from scratch and connecting them to Prospi for cold email outreach.
Want to skip this setup? You can purchase pre-configured inboxes through Prospi at a lower cost with everything set up automatically.
1. Purchase Domains
Buy lookalike or backup domains from GoDaddy, Porkbun, or any domain registrar.
Create one Microsoft 365 account per domain to minimize risk.
Do not create more than 3 inboxes per domain.
2. Create a Microsoft 365 Account
Choose the Business Basic plan or equivalent.
Add your domain during the setup process.
Create an admin user for the workspace.
Keep a record of inbox credentials and their domain mapping.
3. Verify Your Domain and Activate Email
Open the Microsoft 365 Admin Center.
Follow Microsoft's DNS verification instructions.
Set up MX records to enable Outlook email sending.
4. Enable IMAP for All Mailboxes
In Admin Center, go to Users - Active Users.
Select a user, open the Mail tab, and click Manage email apps.
Enable IMAP and Authenticated SMTP.
Save and repeat for all inboxes.
5. Set Up SPF, DKIM, and DMARC
These DNS records are required for good deliverability.
SPF: Add TXT record:
v=spf1 include:spf.protection.outlook.com ~allDKIM: Go to Microsoft 365 Defender Portal - Policies & rules - Threat policies - DKIM. Select your domain and enable DKIM.
DMARC: Add TXT record:
v=DMARC1; p=quarantine; rua=mailto:[email protected]; pct=90; sp=none
[IMAGE: DNS records table with SPF, DKIM, DMARC entries]
6. Authorize Prospi in Microsoft Admin
Go to Microsoft Admin Center - Azure Active Directory - Enterprise Applications.
Click New Application - Create your own application - add Prospi.
Under Permissions, allow the scopes requested by Prospi.
Grant admin consent to finalize.
7. Connect Your Inbox to Prospi
In Prospi, go to Email Accounts and click Add Account.
Select Microsoft as the provider.
Complete the OAuth authorization flow.
Your inbox will appear in your account list once connected.
[IMAGE: Add Account modal with Microsoft option selected]
8. Confirm Setup and Start Warmup
Go to Email Accounts and confirm the inbox shows a green checkmark (authorized).
Warmup starts automatically - no action needed.
Wait at least 2 weeks before launching campaigns.
You can connect up to 3 inboxes per domain. The number of total inboxes depends on your Prospi plan.