Is it safe to send emails from my own server?

There isn’t any problem with sending emails from your own server and you will not get blacklisted by doing so. The problem that some servers are blacklisted only happen when you send more than 500 emails per hour, which include spam content. The spam checker of any email provider is different, but because the emails that you send using Wishlist Membership Notifications are different from one another, in most cases, these emails will not be considered as spam.