Connect an Outlook or Microsoft 365 mailbox

Outlook.com and Microsoft 365 mailboxes connect to Mailnitrix with a Microsoft sign-in. There's no password to copy: you sign in on Microsoft's own page and approve access.

What you can connect

• Microsoft 365 work or school mailboxes, including custom domains
• Outlook.com, Hotmail and Live personal accounts

Step 1: Start the connection

1. In Mailnitrix, open Senders, add a sender account and choose Outlook.
2. Set the daily limit and choose whether to start warmup, then select Sign in with Microsoft.
3. You're taken to Microsoft's sign-in page. Sign in to the mailbox you want to connect.

Step 2: Approve access

Microsoft shows the permissions Mailnitrix is asking for:

• Send mail as you, through SMTP and through Microsoft Graph
• Read and write your mail through IMAP, used only by warmup to find, rescue and reply to warmup emails
• Maintain access, so the connection keeps working without signing in every hour

Select Accept. You're returned to Mailnitrix, the connection is tested, and the mailbox appears with Signed in with Microsoft.

If it says "Need admin approval"

Some Microsoft 365 organisations don't let people approve apps themselves. In that case:

1. Send the approval request to your administrator from the Microsoft screen, or ask them directly.
2. Your admin approves Mailnitrix once for the organisation in Microsoft Entra ID.
3. Select Sign in with Microsoft again.

Step 3: Check limits and warmup

For cold email, 30 to 40 a day is a sensible daily limit for an established mailbox, and new mailboxes should start lower. Make sure warmup is on for new mailboxes; Outlook mailboxes warm up together with your Gmail mailboxes.

"SmtpClientAuthentication is disabled"

Many Microsoft 365 organisations switch SMTP sign-in off. You don't need to do anything about it: if a mailbox returns this error, Mailnitrix switches it to the Microsoft Graph API and keeps sending. Read why this happens.

If you connected the mailbox before Graph sending was available and see a message asking you to reconnect, sign in with Microsoft again for that mailbox to approve the Mail.Send permission.

Removing access

Delete the sender in Mailnitrix to stop using the mailbox. To revoke Mailnitrix's access on Microsoft's side too, open your Microsoft account's app permissions and remove Mailnitrix.