I have to admit I have not read through all the pages of posts.

But, a great tip, it has really made my life so much easier: Get SaneBox. It's an e-mail organizer which is fantastic! It sorts your e-mail into different categories: Inbox (regular mails), SaneNews (newsletter, ads etc), SaneLater (mails that aren't urgent but which you should read), SaneBulk (saves important emails so they don't clutter your inbox, like receipts, bills, plane tickets etc.). It sorts some of this automatic but you can manually change it, you also get an e-mail listing various emails the add-on has placed into SaneLater etc., so you can tell it whether that was correct (by ignoring it) or choosing to move it to Inbox etc.

You can also send yourselves reminders, so the add-on resends the mail to you in two days/a week/a month/whatever.

It is truly fantastic. I use Gmail and it works with that. It has entirely changed how much time I spend shifting through emails, it saves me hours each week, I swear it.