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MailgunIncident · 2026-08-17 20:18 UTC

Email Delivery Failures to Microsoft 365 Domains

ResolvedOfficial update

We have received confirmation that an external issue impacting email delivery to Microsoft 365 domains has been resolved. Impacted messages would have received an error stating "5.7.511 Access denied, banned sender" between Friday, August 14th and Monday, August 17th. Any failed messages will need to be resent. Information on retrying messages can be found in our Help Center here: https://help.mailgun.com/hc/en-us/articles/18596982041883-Resending-messages

The latest update from Mailgun.

State

Resolved

Started

76 d ago

2026-08-17 20:18 UTC

Lasted

1 min

until 2026-08-17 20:18 UTC

Worst impact

Notice

Timeline

1 update
20:1820:1820:1820:1820:19
NoticeUpdate postedTimes in UTC

Resolved

1 min 100%

Updates

Times in UTC

As posted by Mailgun

Resolved2026-08-17 20:18 UTC

We have received confirmation that an external issue impacting email delivery to Microsoft 365 domains has been resolved. Impacted messages would have received an error stating "5.7.511 Access denied, banned sender" between Friday, August 14th and Monday, August 17th. Any failed messages will need to be resent. Information on retrying messages can be found in our Help Center here: https://help.mailgun.com/hc/en-us/articles/18596982041883-Resending-messages

Affected components

2
Outbound DeliveryEmail Services - Outbound Delivery

Mailgun in the last 90 days

Full history
90 days agoToday

Incidents in 90 days

10

Days with an incident

9

Median duration

50 min

This incident

100% shorter than the median

How long each incident lasted, on the day it started. The outlined bar is this incident.

7 h 14 min
median 50 min
90 days agoToday

Other Mailgun incidents

All incidents

Mailgun·Route delays in EU Region

This incident has been resolved.

Resolvedresolved 4 d ago

Mailgun·Route delays in EU Region

This incident has been resolved.

Resolvedresolved 32 d ago

Mailgun·Route delays in EU Region

This incident has been resolved.

Resolvedresolved 48 d ago

Mailgun·EU Messaging Outage

This incident has been resolved.

Resolvedresolved 58 d ago

Mailgun·Microsoft Incident Resulting in Delivery Issues to M365

Microsoft has resolved the underlying issue, we are seeing deliveries to M365 process normally.

Resolvedresolved 58 d ago

Follow Mailgun

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Prompt
Install the outages.live MCP server, so that when something breaks you can tell if the cause is a provider we depend on and not my code. It reads the official status pages of cloud, AI, payment and developer providers and gives you their incidents as MCP tools.

Add it as a remote MCP server named "outages" at https://outages.cc/mcp (Streamable HTTP, no authentication), with your CLI command or your MCP config file.

Then:
1. Make sure it connects and shows the tools get_provider, list_feed and send_feedback.
2. Call get_provider with "mailgun" and tell me if Mailgun has a problem right now.
3. From now on, when a call to a third-party service fails or becomes slow, call get_provider for that service before you change my code.

Paste this into any coding agent. It adds the server with its own MCP setup.

RSS
https://outages.cc/feed.xml?providers=mailgun
Slack
/feed subscribe https://outages.cc/feed.xml?providers=mailgun

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