Because of Spam and Such people try to keep there e-mail addresses private for the fear of unsolicited e-mails. It is a 2 sided thing, you find it more and more common for people to update you with an e-mail address in a Christmas card when most people realise they only have the old home address or contact phone number.
Changing Internet provider also is another reason why e-mail addresses can change.
Your best bet is to send Christmas cards to whom you know with YOUR email address and from there, you can start your new contacts list with e-mail, phone, and mobile.
Its the world we live in.
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Wow Wirral History is coming along Great! Wirral History
we get +200 new members a month now