Don't count mail as unread when its the same as received before

The Problem

I am subscribed to a couple of Wordpress blogs. Anytime the articles are updated, I get a mail. If the same article is updated multiple times, I get multiple mails.

But the mails are same as received before. So if the first mail is not read, all unread mail counts as one. If the first mail is read, subsequent mails are counted as unread.

Proposed Solution

If same mail is received again and if first is read, count subsequent emails also as read.

I know this may not be advisable for all emails. So one option is to restrict it to specific email addresses (to be specified by the user).

(Originally posted by specter78 on GitHub.)