Bizarre failing to send

Use an smtp client plugin like: amazon ses mailer https://www.ads-software.com/plugins/amazon-ses-and-dkim-mailer/

If an email is send successfully depends often on having the same top-level domain for website and mail like [email protected] and https://www.example.com = works.

[email protected] and https://www.sample.com does not work (often)

Well I’ve seen suggestions for the SMTP plugin, but the thing is that it works perfectly fine on website 1, so the server is clearly configured to handle phpmail. Also this form on website 2 DID work fine for months now, only recently it started getting this error. I checked the server’s stack and they haven’t changed anything on me. I’d rather not get additional plugins, especially since phpmail works and this site is bloated enough as it is. Also the website and mail both have the same top level domain.

I understand your concern to not install more plugins than necessary and its weird that is does not work as you said your hosting provider did not update your php version or made other server changes.

You could try to debug the error:
https://www.franceimage.com/en/tech-blog/my-wordpress-does-not-send-emails-anymore/

Every time my mail stuff stop working it’s mostly not the “complex” stuff like WordPress or the plugins that are at fault. It’s mostly that SMTP server isn’t running, no access or wrong credentials.

Make sure that the SMTP server specified in PHP config is reachable and working “telnet SMTPSERVER 25” is one step.