# Mailgun: Email Delivery Failures to Microsoft 365 Domains

> Mailgun status incident “Email Delivery Failures to Microsoft 365 Domains” on 2026-08-17: impact none (vendor’s label), 0 min, 1 update(s). Archived by Rewindex.

Canonical: https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3
Last updated: 2026-08-17T20:18:09Z

- Impact (vendor’s label): none
- Status: resolved
- Started: 2026-08-17 20:18 UTC · Resolved: 2026-08-17 20:18 UTC · Duration: 0 min
- Updates: 1 · Affected components: Email Services - Outbound Delivery, Outbound Delivery
- [Vendor status page: https://stspg.io/mvwg0c62glhf](https://stspg.io/mvwg0c62glhf)
- [Company: Mailgun](https://rewindex.com/company/mailgun.md)

## Timeline of updates

- **resolved** 2026-08-17 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

## Cite this

Status incident (vendor impact label: none) posted by Mailgun, started 2026-08-17 20:18 UTC, resolved after 0 min, 1 update(s).

- Canonical URL: https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3
- Citation: Mailgun, “Email Delivery Failures to Microsoft 365 Domains” (2026-08-17 20:18 UTC). Archived by Rewindex: https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3 (CC BY 4.0).
- Markdown link: `[Mailgun: Email Delivery Failures to Microsoft 365 Domains (2026-08-17)](https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3)`


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Canonical: https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3 · Markdown: https://rewindex.com/company/mailgun/incidents/vwhk7lx3lvs3.md · JSON: https://rewindex.com/api/v1/companies/mailgun/incidents/vwhk7lx3lvs3 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-04T14:48:48.564Z