Microsoft's Outlook and Hotmail spam filters went off piste on Wednesday, dumping an avalanche of unwanted bumf in inboxes.

The snafu was resolved by early afternoon, here in Western Europe.

"Some users may be receiving excessive spam mail," read a warning that briefly popped up on Microsoft's Outlook.com service status page. The glitch lasted around 12 hours, during which time the filters failed to hold back tons of offers for dodgy pills, marriage proposals and other crap from people's email accounts.

Microsoft is in the process of migrating its Outlook.com backend over to its Office 365 service but it’s not immediately clear whether or not a snag in this process caused the problem. El Reg pinged Microsoft’s PR folks for comment but we've yet to hear back.

“On a 'normal' day I might get one to two spams through the filters,” said Reg reader Paul, who first alerted us to the problem. “In the past 36 hours I've had more than 80 spams get through.”

Plenty of Hotmail users took to Twitter to complain about a severe junk mail deluge.

@Microsoft #hotmail what is going on with all the spam and junk emails coming through. Generally pretty good but awoke to 120 in my inbox ? — kal mirza (@howlingcrazy) June 1, 2016

Today's spam count has made me realise what a good job #hotmail are doing all year round. Good work. #spam — Andy Garland (@dennizandy) June 1, 2016

Thank God @Microsoft fixed their Hotmail issue, my inbox was full of SO much spam. — Zack M. (@Zelakto) June 1, 2016

Orlando Scott-Cowley, cybersecurity strategist at email security firm Mimecast, told us: "Excessive spam is not just an annoyance – it’s increasingly riddled with malicious links and malware that can compromise organisations and put valuable data at risk." ®