If you have a trademark then this might be possible, but it depends on what the other application using the name is being used for, whether it is active, etc. Unfortunately we’re not able to reassign names on a general basis. I’d suggest trying an alternative name (I don’t know if Mailbirdapp, Mailbird-auth etc are taken, but those might be possibilities - in general your app name is only going to show up as part of the OAuth flow within Twitter).