This is known as 'phishing ' where the same email gets sent out to many people and the odds are that someone will reply.
There are a lot of different scams going around with the same theme. Either you are a long lost relative of a recently deceased person, you have been chosen to inherit a large amount of money from a person who does not have any living relatives, or maybe you have won on the lottery.
If you were a long lost relative it is unlikely that the executors would make contact with you via email. Is the phone number a mobile? Solicitors and executors of wills do not just hand over large sums of money without very thorough checks, so before you go any further check out the source of the communication. Go and speak to them in person at the Law Firm (if it is a scam it will not have been sent by lawyers at the firm, assuming it is a real firm that has been mentioned in the communication). Make sure they sent the letter. Payment for the execution of a will comes out of the dead person's estate not from the people likely to receive a bequest. It's better to take that sort of trouble than pay out a lot of money on the basis of an email and a phone call to a mobile.
A recent scam is a letter purporting to be from the police confirming the authenticity of a letter regarding a lottery win. This is not true; the police do not authenticate commercial organisations.
DO NOT give out your personal details, bank account details or send any money to anyone who sends you such an email. Many people have been defrauded out of a lot of money. No matter how official it sounds it is highly unlikely that you will receive any money.
If something seems too good to be true then it usually is.
Scam emails, texts and calls can be reported to the National Cyber Security Centre, please see the link in Related Information for details.