I&#x27;ve mostly been happy with Postbox since I moved from Eudora.  It&#x27;s a commercial fork of Thunderbird with some extras.<p><a href="http:&#x2F;&#x2F;postbox-inc.com" rel="nofollow">http:&#x2F;&#x2F;postbox-inc.com</a><p>Alas I&#x27;ve been having problems with v4 (including frequent hanging related to their timeboxing &quot;Time Spent Writing&quot; timer), so I can&#x27;t endorse it as much as I used to.  I&#x27;m also frustrated that the address book doesn&#x27;t include Google Contacts integration.<p>Email is critical to me, and I&#x27;d happily pay $50 - $100 &#x2F; year for the perfect cross-platform email client.  (Postbox is only $15, which is ridiculously cheap for the value I get from it.)