Here is my code:
setUs
I'm using the "Messages Swift Mailer" bundle in Laravel 3 and having the same issue. After some testing, in my case, the solution was to set the same email address that I used in the SMTP authentication on the "from" parameter.
I was trying to use a different address and that was triggering the "swiftmailer expected response code 220 but got code with message" error.
Hope that helps.