Redmine

When user_name is a number you cannot send emails according to email.yml.example

An error occurred while sending mail (can't convert Fixnum into String)

Not working settings:

production:
  delivery_method: :smtp
  smtp_settings:
    address: smtprelaylb.ispgateway.de
    port: 25
#   domain: ispgateway.de
    authentication: :login
    user_name: 20002456
    password: blueberry

Solution: Working Settings with adjusted user_name

production:
  delivery_method: :smtp
  smtp_settings:
    address: smtprelaylb.ispgateway.de
    port: 25
#   domain: ispgateway.de
    authentication: :login
    user_name: "20002456" 
    password: blueberry

You should adjust email.yml.example or fix the code (because finding out this takes some time for a not ruby developer like me). Notice that the same happens if the password is a number (see #2738)