I have a similar issue. All of my email settings seem to be correct.
I have updated WP-Mail-SMTP and Subscribe2 plugins to the most recent versions.
I have set and verified the SMTP settings in Settings > Email. Send test email works.
I have sent Send Email Preview in Subscribe2 and it works.
When I go to Posts > Email Subscribers and attempt to send a test message, this is what happens:
- Select Preview – message is sent and I receive it
- Select Send – get error message: Message failed! Check your settings and check with your hosting provider. Could not instantiate mail function.
- None of my new post email alerts go out
Has anyone seen this error on mailing subscribers when everything else seems to work?