Our main admin shared mailbox M365 now inaccessible

[kennysarmy]

Anyone else withi M365 issues today?

None or our admins can access some of our shared mailboxes 😕

 

Chaos in reception!

 

[ZeroHour]

Does the OWA/Outlook web access work?

https://outlook.cloud.microsoft/mail/{email address}

I think thats the url format but the top right icon on the page has the option to open a mailbox.

[kennysarmy]

I added myself to the affected shared mailboxes at 11.10 - I still cannot get in 25 minutes later.

 

UTC Date: 2026-05-14T10:36:07.647Z
Client Id: 240B37AFCA9A49E6A51AE57952A4741F
Session Id: dfc543a0-319f-469b-814a-cd6ddd128c6b
Client Version: 20260501001.17
BootResult: accessDenied
Back Filled Errors: Unhandled Rejection: Error: 500:undefined|undefined:undefined
err: Microsoft.Exchange.Data.StoreObjects.AccessDeniedException
esrc: StartupData
et: ServerError
estack: Microsoft.Mapi.MapiExceptionNoAccess
st: 500
ehk: X-OWA-Error
efe: LO2P265CA0114
ewsver: 15.20.9891.14
reqid: c0417cbe-47ac-bb02-e04d-56efd1f9731b
cv: vvLbzl3w53/Ytar5gSiA0L.0.1.1
emsg: ErrorPermissionDenied

 

 

Admin staff can now access the shared mailboxes but are reporting that they are incredibly slow  and some email previews just showing grey boxes!

[ZeroHour]

Adding permissions to a mailbox can take a while to roll out depending on how big the mailbox is.

Is there anything in your Service Health dashboard?

May be worth reporting to MS. Is all other email/owa fast and working?

[Gaznae]

We have no issues today.

[kennysarmy]

So I went back in to the two shares mailboxes an hour later and neither had my name still in the access lists  - not only could we get in the mailboxes but it looks like no changes could be made either, even though it showed my name in the access list after I added myself.

 

Admin team now reporting they are working again, ableit slowly and after readding myself back in again they are both now opening for me.

 

Grrrr