maybe add docs about env settings overlap : -port in GRAYLOG_SMTP_SERVER == won't start about graylog2-images

[scorpp]

Similar issue here - a docker container was set up without smtp setting specified first. Afterwards we needed alerts, but adding GRAYLOG_SMTP_SERVER has no effect

[mariussturm]

I improved the options parsing for GRAYLOG_SMTP_SERVER a little bit. Now the command should fail if you provide -port instead of --port. Same goes for a missing SMTP server like "localhost --port=25" vs. "--port=25".

@scorpp if you change something on the container settings you need to recreate the container. Use the data persist option for this: http://docs.graylog.org/en/latest/pages/installation/docker.html#persist-data
Then it's easy to start a new container with changed options on-top of old data.