The e-mail could not be sent your host may have disabled the mail() function

Replies: 0

Hi
A customer was having their WP emails go into spam. We thought we would try your SMTP plugin. I installed it and used your test email function and it worked OK. I could see in the mail headers it was sent through the SMTP server.

but other mail forms on the site, like WooCommerce order notification and forms and not being received. Using forms on the site shows this error:

The e-mail could not be sent
Possible reason: your host may have disabled the mail() function

So do you know why no forms or emails are working please, when your test function works OK?
Thanks
Laurence