platform.sh hosting email issues - Expected response code 220 but got code ""

Laravel Version: 5.5.19 PHP Version: 7.1

Hi,

The following issue is only on Platform.sh hosting, they cannot offer much help as it seems to be an application issue.

When sending mail using the sendmail driver I always receive this error: "Expected response code 220 but got code "", with message "" " I am using the standard Mail::send facade to create this email.

When I use the standard php mail function the emails work fine mail("[email protected]", "My subject", 'some message here')

I have seen lots of bugs regarding laravel 5.5 and email errors around the internet but none of them include a fix.

Does anyone have any idea what could be causing this?

Thanks for your time.