Kendo - 11:50 pm on Mar 25, 2013 (gmt 0)
anyone remember a time when some sites wouldn't accept signups from email addresses?
Sure do. In fact we used to reject mail sent from web forms using Hotmail addresses. Even today, if someone is using a free mail service, we realise that they are not using their domain mail address and probably have many different disposable email addresses. So many in some cases that it takes weeks for them to find your support response.
If your clientele are companies, allowing them to use disposable email addresses for purchases and support is an absolute waste of time. How in the blazes will they ever get proper support and be advised of critical software updates?
With ISPs the old address can disappear
Not if they are using an email based on their domain. After all, if your clients have web sites and email @ their domain, why settle for anything else. What else can they expect when seeking your expert advice at the expense of your time? So they should at least use a legitimate email address.