Email Error: Could not instantiate mail function. Please check Admin->Configuration->Email Options->Email Transport.


This error is ruining my website for no apparent reason. The site stopped sending emails to me but did allow transactions. Now it will not let anyone register, it cannot retrieve passwords for those who forgot, nor will it send emails.

I have checked the settings so far and have found nothing different. Its set to PHP has worked perfectly till THIS WEEK.

The ONLY thing I did change was I added a similar domain name that redirected to the main site. I just took this feature away.

Any suggestions? I rely on this site so this is super important I get it fixed.