How to send emails with multiple, dynamic smtp using Actionmailer/Ruby on Rails

Question

I saw this post but mine is slightly different:

Rails ActionMailer with multiple SMTP servers

I am allowing the users to send mail using their own SMTP crede

Answer 1

Doing what is described in the other answer is not safe; you are setting class variables here, not instanced variables. If your Rails container is forking, you can do this, but now your application is depending on an implementation detail of the container. If you're not forking a new Ruby process, then you can have a race condition here.

You should have a model that is extending ActionMailer::Base, and when you call a method, it will return a Mail::Message object. That is your instance object and is where you should change your settings. The settings are also just a hash, so you can inline it.

msg = MyMailer.some_message
msg.delivery_method.settings.merge!(@user.mail_settings)
msg.deliver

Where in the above mail_settings returns some hash with appropriate keys IE

{:user_name=>username, :password=>password}