Docker container has problems sending emails after signup

[Chris-Schnaufer]

There is an error reported to the user of the web site after signing up for an account when running the docker image. The account gets created however. This indicates that the problem arises from attempting to send email. The error reported to the user is We're sorry, but something went wrong. We've been notified about this issue and we'll take a look at it shortly. The exception message (which I can't find right now) indicates that the problem occurs when trying to bind to port 25.