EmEditor features the ability to convert MIME encoded-word header values to readable text. Emails are encoded using the MIME specification to be able to include Unicode characters. When you view email headers encoded in MIME, it will look something like this:
Subject: =?UTF-8?B?W0VtRWRpdG9yICjjg4bjgq3jgrnjg4jjgqjjg4fjgqPjgr8pXQ==?= =?UTF-8?B?IOOCqOODs+OCs+ODvOODieOBruWumue+qeOBq+aXouWumuWIhui/veWKoA==?=
EmEditor shows the decoded text and gives you the option to convert all encoded-words to readable text.