A "third-party routing issue" prevented fixed-line users of TPG Telecom and its brands from accessing Office 365 and other Microsoft services.

The issues started at 9.45 AEST, with users turning to internet forums to report that Office 365 services were inaccessible.
However, users were able to access the services via cellular connections, which led to suspicions that the root cause was with a particular provider, rather than being with Microsoft.
TPG Telecom confirmed to iTnews an “earlier issue impacting Microsoft services for TPG fixed lined customers” but noted it had since been resolved.
Some users reported services beginning to resume within the hour. It appears the services are now functioning normally.
Microsoft has suffered a series of Office 365 outages over the past year, mostly around authentication but also some stranger ones, such as routing all inbound email to junk.
The story was updated at 1.00pm to reflect the cause being with an (undisclosed) third-party.