The config file:

sudo vim /usr/share/redmine/config

Related links:

http://www.redmine.org/projects/redmine/wiki/HowTo_Install_Redmine_25x_on_Ubuntu_1404_with_Apache2_Phusion_Passenger_MySQL_and_Subversion //good

http://blog.csdn.net/pochuanpiao/article/details/12840985 //good

http://www.redmine.org/projects/redmine/wiki/EmailConfiguration  //email configuration

http://www.aiezu.com/code/exchange2010_smtp_unrecognized_authentication_type.html  //504 5.7.4 Unrecognized authentication type

http://xianghuaclm.blog.163.com/blog/static/66687832012046921370/

ubuntu + redmine + email--setup