Did the deceased use email?
Does the wife or brother know the password?
Is the property jointly owned by the wife and the deceased?
If “yes” to all three, why not continue to use that email account and have the brother sign off his emails with the wife’s name?
Make clear in the first email to the strata manager that following the passing of her husband, the wife will now do the correspondence. For simplicity, inform the strata manager and committee members that the family will keep the deceased email address.
Just my 2 cents.