codeception/verify 2.1 removed support for expect()->stringContainsString() so we need
to replace it with verify()->stringContainsString().
[MAILPOET-5664]
Some hosts do perform intentional misconfiguration of the mail function, causing it not to work.
When the mail function is misconfigured, we can still access and execute the mail function from within the codebase, but we get an error.
There’s no accurate way to know the PHP mail function is misconfigured. Unless we execute the function with all the proper parameters and check the exception error message against this error `Could not instantiate mail function.`
MAILPOET-4760
