8. A computer implemented method for assisting email users of an email system, comprising; providing an address store and email store for a user; gathering email addresses from a plurality of data sources including stored email; monitoring email correspondence for a user including constantly scanning new inbound emails to the user on receipt and outbound emails from the user; extracting one or more email addresses from each email message associated with the user in the plurality of data sources, and the inbound and outbound messages; determining a relevance to the user of one or more addresses extracted from the data sources or email messages, the relevance being determined based on a heuristic evaluating an appearance of the one or more email addresses relative to other email addresses, wherein determining the relevance based on the heuristic further comprises: computing a percentage of known email addresses to the total number of known email addresses and unknown email addresses in each of the inbound messages and outbound messages addressed to the user; assigning a relevance weight to the unknown email addresses in each of the inbound emails and outbound emails based on the percentage; and marking the email addresses in each of the inbound emails and outbound emails that are unknown as relevant if the relevance weight exceeds a pre-determined value; and based on said determining step, upon input of an address by a user into an email composition user interface, altering the interface to display a visual indicator to indicate potential email address problems to the user.
11. The method of claim 8 wherein the step of determining includes marking any email address as relevant and applying a subtraction algorithm.