Question: Which mail server should I use to send mail through with my forms?
You should use relay.hostinguk.net
(Note that this will not work from any other server other than our own, so external testing (not on our network) of this server will fail.)
With each hosting plan you will get a mail service. For some you can use localhost, however in most cases you will be required to Authenticate with an email address and password and you will also be limited by the outgoing mail limits of the plan.
Using this may also cause issues when sending to other accounts on the same domain where you mail is hosted elsewhere as the server will try to deliver internally meaning it'll likely never reach your mailbox.
We also have a relay server relay.hostinguk.net specifically for this. This is an open relay server for our network, meaning if you are on a shared server you can relay through this without the need to authenticate with a username and password. External testing won't work outside of our network as this is locked down for obvious reasons.
Encryption: TLS is available.