530 5.7.57 Client not authenticated to send anonymous mail during MAIL FROM
The app sent to smtp.office365.com without logging in
Seen in Microsoft 365 SMTP client submission, .NET SmtpClient, printers, scanners
The device or application connected to smtp.office365.com, which only accepts authenticated submission, but sent MAIL FROM without a successful login.
Common causes
- No username and password (or OAuth token) is configured in the app or printer.
- Authentication failed silently, often because SMTP AUTH is disabled; look for a 5.7.139 error alongside it.
- The device does not support SMTP AUTH or STARTTLS on port 587.
How to fix it
- Enter the mailbox credentials in the app and use port 587 with STARTTLS.
- If authentication is failing, fix that first (see 535 5.7.139).
- For devices that cannot authenticate, use direct send to your MX endpoint or an SMTP relay connector instead.
Got a different message? Paste it into the error explainer.
Related errors
- 550 5.4.1 Recipient address rejected: Access denied · Microsoft 365 rejected an unknown recipient at the edge
- 550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP · Microsoft 365 blocked the tenant's outbound mail
- 535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant · Microsoft 365 refused the SMTP AUTH login
- 550 5.7.520 Access denied, Your organization does not allow external forwarding · Automatic forwarding to an outside address is blocked
- 550 5.1.8 Access denied, bad outbound sender · The sending account was blocked for spam
- 451 4.7.500 Access denied, please try again later · Microsoft 365 is temporarily throttling the sending IP
- 552 5.2.2 The recipient's inbox is out of storage space · The recipient's mailbox is full
- 552 5.3.4 Your message exceeded Google's message size limits · The message is larger than the server accepts
- 535 5.7.8 Username and Password not accepted · The SMTP login was rejected
- 450 4.2.0 <user@example.com>: Recipient address rejected: Greylisted · The message was greylisted; it will be accepted on retry
- 553 5.7.1 <user@example.com>: Sender address rejected: not owned by user · You logged in as one user but sent as another address
- 530 5.7.0 Must issue a STARTTLS command first · The server requires TLS before it accepts mail