DOAJ says that uploaded files should not contain the author email addresses in the article’s metadata due to data privacy issues (https://doaj.org/publishers, paragraph 9):
PLEASE NOTE that DOAJ does not want author email addresses. We kindly request that you DO NOT send any email addresses to us in metadata uploaded to us. These should be stripped out before upload as XML or via the API. Recent guidelines on the use of personal data restrict what you can send us.
In OJS 3.1.1-4, author emails are still in the xml file.