# Exchange Online SMTP AUTH Is Ending: Final Action Plan

> Microsoft has confirmed the final shutdown of SMTP AUTH and basic authentication in Exchange Online. Here is the deadline, what breaks, and the migration checklist for every legacy app, printer and service account in your tenant.

Source: https://loopbackup.com/blog/exchange-online-smtp-auth-deprecation-action-plan
Publisher: Loop Backup
Content language: en

---

## At a Glance

Microsoft is permanently disabling SMTP AUTH client submission in Exchange Online for all tenants in the next enforcement wave. Anything still relying on legacy authentication, multifunction printers, on-prem monitoring tools, legacy CRM connectors, "send as" scripts, will stop sending mail.

This is the same playbook Microsoft used for EWS: a soft default-off, then a hard cut-off. The previous waves disabled basic auth for IMAP, POP, MAPI, EWS, OAB and PowerShell. SMTP AUTH is the last protocol standing.

## Why this matters for backup and continuity

Most cloud backup vendors no longer touch SMTP AUTH, but plenty of *internal* automation does:

- Scheduled report mailers that send straight from a shared mailbox
- Backup status notifications from legacy on-prem agents
- Printer scan-to-email using a tenant mailbox
- Line-of-business apps with hard-coded credentials
- Monitoring tools (PRTG, Nagios, older Zabbix versions)

When these stop sending mail, on-call alerts disappear silently. Test before the deadline, not after.

## What replaces it

Microsoft recommends:

1. **OAuth 2.0 with the SMTP AUTH protocol** for apps you control
2. **High Volume Email for Microsoft 365** for transactional senders
3. **Microsoft Graph sendMail API** for modern application code
4. **Direct Send or a relay connector** for printers and IoT devices that cannot do OAuth

If your vendor cannot offer any of these, that vendor is end of life.

## How [Loop Backup](/) handles this

[Loop Backup](/microsoft-365-backup) uses Microsoft Graph and modern OAuth across every integration. We never depended on SMTP AUTH for backup, restore, or notifications, so this deadline does not affect your backup posture, but it absolutely affects the rest of your tenant.

If you need a sanity check on which legacy connections are still active, the Exchange admin centre report "Users using legacy authentication" lists them all.

## Bottom line

This is the easiest deadline to miss because it does not generate user-facing errors, only silent mail failures. Run the inventory now while there is still time to re-platform the noisy ones.