Sorry you’re having some trouble here! To get started, can you first clarify what you mean here:
Nothing changed on the Database or FTP files, just a regular transfer.
If you didn’t change the database or the files, how did you pull off this transfer? Just curious about what did change…
Next, I’d recommend contacting your web host about this (Hostgator). The issue may unfortunately be something with their configuration, email can be configured or limited by hosts in certain ways. Contact them directly and ask if there are any limitations with PHP’s mail() function or WordPress’ wp_mail() function on their servers…
Let us know what you find out from them!
Thank you,
George