A notice from Microsoft said: "Dynamics 365, LinkedIn, and other services that leverage Azure Active Directory are, or were, also affected by this event."

The issues began at 9.15pm UTC on Tuesday, 29 January (8.15am AEDT on Wednesday).

The company said the preliminary root cause was degradation of a portion of third-party managed network infrastructure that facilitates authentication requests and access to Microsoft 365 services.

Last week, users of Microsoft Office 365 and Microsoft 365 in Europe were unable to access their mailboxes for more than a day, with a borked domain controller apparently being the reason.

In November last year, Microsoft had issues with the Office 365 service, with customers complaining they were unable to sign in to their accounts.

A number of cloud services offered by the Redmond software giant use the MFA offered by Azure Active Directory to authenticate by default.

Two days before that, users of the company's Exchange Online service were unable to access their email for more than 12 hours.

And a week prior, Microsoft cloud customers using multi-factor authentication found themselves locked out of their accounts.

Additionally, a lightning strike near one of Microsoft's South Central US data centres in September led to a massive outage in regions around the globe.

The Azure service was hit by a fire suppression incident in 2017. It also suffered prolonged downtime in 2013.

Commenting on the outage, Garrett O'Hara, principal technical consultant at email and data security company Mimecast, said: “The outage is just another in a slew of outages plaguing the platform that serves as a reminder for organisations that operational dependency on any one environment creates unnecessary business risks.

"While the 0365 outage is fresh in our minds it is worth businesses taking a few minutes out to do a ‘back of an envelope calculation’ of what the outage cost them this morning – the collective cost of downtime will run into millions of dollars in lost productivity.

"No organisation should trust a single cloud supplier without an independent cyber-resilience and continuity plan to keep connected and prepared during unplanned, and planned, outages.”

Update, 31 January, 5am: A Microsoft spokesperson said: "We’ve fixed the delay some customers may have experienced accessing cloud resources."