I recently started getting this error
Godaddy server
http://thegallery.us/temp/2021-12-21_073512.jpg
form:
http://www.thegallery.us/form/title/index.php

You need to redo your settings for the stamp manual thingies in the user config PHP file, not at my pc at the moment so I can't do much more, there is a help thing about this on cc which sort of says how to

It may be that the first post at
https://www.coffeecup.com/forums/web-fo … h-godaddy/ would be relevant. The article referred to has been updated in 2020, and is at https://www.coffeecup.com/help/articles … m-builder/ . I suspect that's the one mentioned by Wayan.

Frank

how do I find the hosting provider's requirements?

ask the support from your provider
you may find that its a matter of renaming your email server requirements

godaddy sent me to this page
https://www.godaddy.com/help/send-form- … server-953
I'm on Linux (cPanel)
What do I do now?

Do you not understand Indonesian

Linux (cPanel)
Gunakan localhost, kecuali jika:

Anda menggunakan skrip PHP dan fungsi mail().
Anda menggunakan skrip Perl dan biner /usr/lib/sendmail.
Dalam kasus tersebut, Anda tidak perlu menentukan server relai.

I suspect you need change your STMP in the forms user settings to
Local host the mail serve address
as per the link to the instructons given by Frank
edit this file
user.cfg.php