Ok, really weird problem - we've tried all the other solutions in the form, none have helped.
Password reset emails to customers AND New Client Notifications to administrator are NOT being sent. All other emails, invoices, credit card payment notices, etc... are being successfully sent. The weirdest part - If we go in and do a "Reset & Send Password" from the admin area, we get a confirmation from WHCMS that it was successfully sent, however it never shows in the email logs or under Recent Emails. It shows as successful in the Activity Log, but there's nothing in the Email Log.
We've tried switching from PHP mail to SMTP - no help
WHCMS 7.7.1, PHP V 7.1.14
Thanks.