Rails 2.3.14 is not completely Ruby 1.9.2 compatible.
Specifically the vendored version of TMail in ActionMailer calls String#is_binary_data?. This method was removed from Ruby in 1.9.2.
I realize that this probably won't be fixed as Rails 2.x is EOL, but I'm just putting it out there in case other people run into the problem. Personally I'd advocate a fix, Rails 2.3 promised Ruby 1.9 compatibility and this breaks that promise.
A simple workaround is to copy the definition of the method forward and add it to the String class in an initializer.
Here is it for reference (copied from apidock.com)
If you load Psych before loading Syck, this method will not exist on
String because Syck will never be loaded. There are three ways to work
around this without changing Rails. First would be to require
'syck/rubytypes':
I don't recommend this solution because it can impact YAML dumping and
loading. The second solution would be to freedom patch the method
yourself:
class String
def is_binary_data?
encoding == Encoding::ASCII_8BIT
end
end
I recommend this solution.
The third solution is to downgrade Rubygems. It's likely rubygems is
the one loading in Psych before Syck. But it could also be bundler. It
could be many things, so I don't suggest this solution.