Redmine

Shouldn't be the username of your google apps account

You need to remove tls: true with Redmine 2.0+

My configuration doesn't have single quotes around the port. Also, for authentication I'm using ":plain" not ":login" and you appear to have a space between the : and login.
Also, spacing is important, you need to follow the spacing below (no tabs)

production:
  email_delivery:
    delivery_method: :smtp
    smtp_settings:
      tls: true
      enable_starttls_auto: true
      address: "smtp.gmail.com" 
      port: 587
      domain: "smtp.gmail.com" # 'your.domain.com' for GoogleApps
      authentication: :plain

Do I need smtp_tls to be installed for this to work?
I tired your suggestions but still its not working.

I tried this:

production:
email_delivery:
delivery_method: :smtp
smtp_settings:
address: "smtp.gmail.com"
port: '587'
domain: "collabnix.com"
authentication: :plain
user_name: "info@collabnix.com"
password: "password"

but it threw error:

Your Redmine configuration file located at /usr/local/share/redmine-2.0.3/config/configuration.yml is not a valid YAML file and could not be loaded.

OK, you still have quotes for the port number.
Have you matched the spacing as outlined in my previous post? If the idents are done properly (spaces only, no tabs, each level is 2 spaces), then it won't be recognized as a valid yml file.