In order to safeguard our servers from spammers, we’ve removed the ability to send e-mails directly from WordPress on sites hosted with LaunchCDN.
For most Private Blog Network sites hosted on WordPress, this shouldn’t be a problem. You’ll always be able to login to your WordPress sites from the Dashboard, but if you want to get e-mail notifications from plugins or other services on your blogs, then you’ll need to install a plugin to send e-mail via an API.
SMTP2Go are a popular e-mail delivery provider, used by brands like HP and Virgin Active. On their Free Plan, you’re able to send up to 1,000 emails per month forever, at no cost. Much like Mailgun and SendGrid, SMTP2Go also offer a free SMTP2Go Plugin for WordPress which you can use to send e-mails over their HTTP API.
Simply create a free account with SMTP2Go, install their plugin and configure the API key, and you’re set.