Yahoo is probably the worst "big name" free email provider, as they regularly block legitimate emails for whatever reason. Their spam filters are extremely unreliable and my emails often never arrive. This happens quite often, so if you're using Yahoo email and aren't getting the emails you expect from me, then chances are Yahoo is blocking my emails. This occurs usually because of the combination of keywords. If this is happening to you, please use gmail to contact me, and use the email exclusively for contact with me. Best not use your ISP email as this will change if you use a different ISP.
