In the online Mega docs you can find the section that links you to the API documentation. Both links are pasted below.
I have also attached a screenshot of the specific method that I believe you are looking for. I hope that this helps.
Don't have documentation, but best i can do is share this script in case you need something like this urgently.
strEMail1 = email@example.com
strEMail2 = firstname.lastname@example.org
Set omailer = CurrentEnvironment.Toolkit.MegaMailSender
omailer.Subject = "Test of mail sending (subject)"
omailer.Sender = strEMail1
omailer.EnableHtml = TRUE
omailer.Body = "Test of mail sending (body)"