No mail send after update from swiftmailer

Make sure that your hosting supports this. I was having the same issue on Acquia and after some research, I found it only supports the -t flag. If your hosting doesn't support the -bs flag, you can configure a new sendmail command in your settings.php file.

This is the documentation for Acquia I followed.

Hopefully this is now fixed

Had this error.
Easiest way to resolve was to remove "Sendmail" as a transport policy option and add "Native" instead.
Change policy at Home -->Administration -->Configuration -->System-->Mailer policy

Automatically closed - issue fixed for 2 weeks with no activity.

Is there any more advice on how to fix this on Acquia?

I found this document → that explains adding sendmail commands to settings.php.

But what commands should be added?