Looks like another host not adding default php mail() function
You’d have to ask tech support of that host to enable it, or try to switch to an smtp mailer.
For the records: php mail() is not per se insecure.
What can be insecure is the form not validating or giving access to anyone (speak: spam).
I’ve written some instructions back in time here to add smtp mailer Mail problems - #23 by smileBeda which could help… but it’s pretty technical stuff