Umm...do you really want to share your address list with god knows who
, and not knowing what they might do with it, just to avoid using an app? What would the people on your list think if they found out you were doing this?
If you need to do mailings via an online service, at least go with a reputable service like MailChimp
who enforces reasonable rules to protect your list's privacy, and also make sure you stay compliant with things like the CAN-SPAM Act so your sending address doesn't get blacklisted.
MailChip has free packages. And their paid packages are very reasonably priced.