I have a shop of non tangible products that i deliver them via e-mail. I am using yahoo as sender. Until today i have had no problems with it, when a client told me that he had not received his goods, and he's e-mail was hotmail. I send those good by responding to the paypal receipt. I have tried 2 or 3 times to send him but no success. After that i tried to send him to gmail which worked. Can you please recommend me a good e-mail sender that it won't make my e-mails get blocked?