Is 550 5.7.501 permanent or temporary?

550 5.7.501 is a permanent (5.x.x) failure — the server will not accept the message as-is, and retrying without changing anything won't help. You need to fix the underlying cause.

Is this my problem or the recipient's?

It depends on the cause — the account was compromised is the most common. Work through the causes below to find which applies to you.

How do I check my sending setup?

Run a free EmailHealth check on your domain — it verifies SPF, DKIM, DMARC, blacklist status, and more in a couple of seconds, which covers the most common causes of delivery failures.

550 5.7.501 — Access denied, spam abuse detected (Microsoft 365)

Access denied, spam abuse detected (Microsoft 365)

A 550 5.7.501 from Microsoft 365 says "Access denied, spam abuse detected". Codes 5.7.502 and 5.7.503 say "Access denied, banned sender". In all three, Microsoft banned the sending account because it detected spam.

Updated June 13, 2026

SMTP Exchange / Mail Log

> MAIL FROM:<you@yourdomain.com>> RCPT TO:<recipient@example.com>✕ 550 5.7.501 Access denied, spam abuse detected (Microsoft 365)

550 5.7.501 is a permanent SMTP reply meaning access denied, spam abuse detected (microsoft 365). Microsoft says to make sure the account problems are fixed, reset the account credentials, and then contact Microsoft Support through your normal channel to restore sending.

What 550 5.7.501 means

Microsoft says to make sure the account problems are fixed, reset the account credentials, and then contact Microsoft Support through your normal channel to restore sending.

⚠️

This is a 5.x.x permanent failure — the message will keep bouncing until you fix the cause. Retrying the same message unchanged won't help.

Common causes

📨

The account was compromised

Most common

Someone used it to send spam or phishing.

🔁

Bulk or cold email from a normal mailbox

Common

Large volumes of unsolicited mail from a Microsoft 365 user account.

⚙️

An app with access to the mailbox sent mail

Less common

A connected tool sent more than expected.

How to fix 550 5.7.501

1
Secure the account
Reset the password, revoke sessions, turn on MFA and remove unknown rules and app access.
2
Contact Microsoft Support
Microsoft restores sending only through support after the account is clean.
3
Move bulk sending elsewhere
Use a sending service and separate domains for campaigns, and monitor those domains.

Confirm your domain is set up correctly

Most delivery failures — permanent or temporary — trace back to authentication or reputation. Run a free EmailHealth check to confirm SPF, DKIM, DMARC, blacklist status, and TLS are all healthy for your sending domain. If you send in volume, free daily monitoring will alert you before a small issue becomes a flood of bounces.