Last Christmas I sent a greetings email to all member who have not disabled admin emails. A number of these were returned as undeliverable, but I did'nt know about this until they were sent to my mailbox when the site came back online after last month's outage.
A small number of members have been deleted because the email addresses associated with these accounts is invalid and have been inactive for over a year. Those with a broken email address but have been active within the last year have not been deleted. Instead I have removed the broken email address from the account settings.