We use Netwin's FTP software here and SSL.
We don't use the default DNS Server software.
We don't use Wordpress.  Do a google search on Wordpress hacks.
Each website has an account on Surgemail, and are set to 250 per day max.
If an account holder needs more than that, then they are provided with a key that closely matches the size of their mailing list. You control these by assigning the email accounts to a Group.  Setup groups then put people or servers into a group.

BarryZ