You can set a different title for your MFMailComposeViewController with a single line, like so.
...
[self presentModalViewController:controller animated:YES]; // Existing line
[[[[controller viewControllers] lastObject] navigationItem] setTitle:@"SomethingElse"];
...
However, this implementation effectively relies on undocumented features of MFMailComposeViewController. You're accessing the navigationItem of a private class (_MFMailComposeRootViewController) and changing its title to something other than the mail subject. I echo Art Gillespie's sentiment in that you should not do this and are very likely to be rejected by the Apple reviewers for doing something like this. In addition, this process could change completely in any minor point release of the iPhone OS, possibly causing crashes for your users until you can release an update to fix the behavior.
The decision is up to you, though, and if you still want to take these unrecommended steps, that is how you do it.
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