Outlook · Microsoft 365
Outlook that keeps sending when SMTP stops.
Sign in with Microsoft and you're connected. No passwords to copy, and if Microsoft has switched SMTP off for a mailbox, Mailnitrix moves it to the Graph API automatically.
Setup
One sign-in. That's the setup.
- 01
Sign in with Microsoft
Add a sender, choose Outlook and sign in on Microsoft's own page. Mailnitrix never sees your password.
- 02
Approve access
Allow Mailnitrix to send mail and read mail for warmup. Some organisations need an admin to approve once.
- 03
Ready to send
The connection is tested straight away. Set a daily limit and switch on warmup if the mailbox is new.
Microsoft Graph fallback
When Microsoft turns SMTP off, you don't notice.
Microsoft has been switching off password-based and SMTP sign-in across Exchange Online, and many organisations disable SMTP for individual mailboxes. When that happens, most sending tools simply fail.
- Mailnitrix spots the "SMTP disabled" response the first time it appears
- The mailbox switches to the Microsoft Graph API and the email is retried
- Every later email from that mailbox goes through Graph
- Other mailboxes and providers are unaffected
priya@tryyourco.com · attempt 1 · SMTP
535 5.7.139 SmtpClientAuthentication is disabled for the Mailbox
priya@tryyourco.com · switched to Microsoft Graph
202 Accepted · sent to omar@tailspintoys.com
next emails from this mailbox · Graph
Built for Microsoft
What Mailnitrix does for Outlook mailboxes.
- Sends from your real mailbox, so replies arrive in Outlook
- Warmup rescues emails from the Junk folder
- Tokens refresh on their own; reconnect only if access is revoked
- Mixes with Gmail mailboxes in the same campaign
Before you send
Set up your domain.
- SPF and DKIM for your Microsoft 365 domain
- A DMARC record, at least p=none
- Microsoft requires all three from senders of more than 5,000 emails a day to Outlook.com
- Use a separate domain for outreach to protect your main one
FAQ
Outlook questions.
Do you store my Microsoft password?
No. You sign in on Microsoft's own page and Mailnitrix receives a token that can only do what you approved. Tokens are encrypted at rest and you can revoke them from your Microsoft account at any time.
What does "SmtpClientAuthentication is disabled for the Mailbox" mean?
Microsoft or your administrator has switched off SMTP sign-in for that mailbox. Many tools stop working at that point. Mailnitrix detects the error and sends through the Microsoft Graph API instead, with no action needed from you.
It says I need admin approval. What do I do?
Some Microsoft 365 organisations don't let users approve apps themselves. An administrator can approve Mailnitrix once for the organisation, and then everyone can connect their own mailbox.
Are personal Outlook.com and Hotmail accounts supported?
Yes. Personal Microsoft accounts and work or school Microsoft 365 accounts both connect the same way.
How many emails can an Outlook mailbox send?
Microsoft 365 allows up to 10,000 recipients a day per mailbox, and personal Outlook.com accounts allow far fewer. For cold email, stay around 30 to 40 a day per mailbox once it's warmed up.
Start sending smarter, for free.
1,000 emails every month on the free plan. No credit card, no time limit.