mikel/mail — pull request #420 by ippeif (2012-07-18 06:45:35+00:00)
Title: Address#address= should cause reset some parsing/formatting cache 

```ruby
irb(main):001:0> addr = Mail::Address.new 'local-1@domain-1'
=> #
irb(main):002:0> addr.address = 'local-2@domain-2'
=> "local-2@domain-2"
irb(main):003:0> addr
=> #
```

As above, setting `local-2@domain-2' affects only its domain part.

I think Address#address= should cause reset (to nil) some instance variables.