The company, which has millions of customers, blamed a "temporary technical error" for the incorrect emails.

It stressed that the wrong name in the email greeting was the only mistake and no personal details had been compromised.

Michael has recently slipped in popularity among baby names.

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One accidental Michael, a life insurance customer whose real name is Andrew, said he was worried that the mistake may have signalled other errors.

"The irony is I hadn't noticed the original 'Michael' email, it was this follow up that caught my eye," he said.

"Getting a first name wrong is one thing, but what if it was my data - my address or policy information - being sent to someone else instead?"

Aviva said customers, of any name, should not be concerned as there were no wider privacy issues.

"We sent out some emails to existing customers, which, as a result of a temporary technical error in our mailing template, mistakenly referred to customers as 'Michael'," a spokeswoman for the company said.

"We've apologised to these customers and reassured them that the only error in the email was the use of the incorrect name as a greeting. There was no issue with personal data; the remainder of the email and its content was correct."

Perhaps inspired by Michael Jordan, it has been a popular first name

Michael was one of the 10 most popular boys' baby names in England and Wales, from the 1930s to the 1980s.

However, its popularity has waned since, falling well behind the likes of Oliver, George, and Harry.

The latest figures from the Office for National Statistics (ONS) show 869 babies born in England and Wales in 2018 were named Michael. That left the forename 74th in the rankings of boys' names, down six on the previous year, but falling 22 places compared with 2008.

It remains a popular second forename in Scotland, ranked 10th for boys in 2019, but was ranked 72nd as a first name.