For the past 7 years, I have used Apple’s standard email setup-- Mail App paired with iCloud Mail service. However, search recently broke, and I spent time trying to fix that, which led me down the path trying to better my email workflow. First step was creating folders and setting up server side email filter on iCloud.com. Next, I was wondering what to do about attachments-- Mail Drop allows you to send big attachments via a link, but what about past attachments, and Mail Drop deletes attachments after 30 days, I think. Finally, I was wondering whether I should export my entire email library to my Mac-- would search run better? Any tips or favorite applications, utilities, or services would be appreciated. I looked at the Mac Power Users episodes but I don’t think there has been one about email for awhile. Thank you!
I’ll reiterate my opinion that email makes for a poor filing system. Many people here discuss about various systems for organizing research, notes, documents, etc yet maintain a huge vat of email stew. As you found, search can be a problem. Backup granularity is often a problem with no way to restore a single email with an attached document. Finally, how often do people’s email violate a company’s document retention policies? Discovery in legal proceedings have uncovered many embarrassing emails.
I think a better approach is to decide on a document management system and export your emails into that system. It can be as simple as a folder hierarchy or tools like DevonThink or EagleFiler.
How often have you replied to or forwarded an email that’s more than 6 months old? If never, why do you need to keep it as an email?
I’m in the same camp as @glenthompson when it comes to email. Things like invoices and receipts get saved into DEVONthink on my Mac, as do any conversations that I want to preserve. If there’s an action I need to remind myself to do as a result of an email, I’ll make a calendar or reminder item then delete the email (obviously copy any pertinent info first!)
Organising email is one thing, but I’d suggest taking a step back and looking at what emails you’re getting and whether you actually need them. If not, unsubscribe (if it’s a mailing list) or change your delivery settings at whichever site is sending.
I switched from Apple Mail to MailMate on the Mac a while ago, and it really helped me to both work out where email was coming from and also automate some of the handling of it. (Apple Mail can automate some things using rules, but MailMate takes it to another level.)
I now keep very little in my email inboxes, and usually only for short periods of time while I’m deciding how to process them. All archived emails go direct to DEVONthink.
Adding to this that I’ve heard people who think IMAP is a “backup”. And it’s not. It’s a sync. So if your computer falls in the river, you can always re-download - but if there’s an IMAP error or the server has a problem, your local copy will helpfully delete itself as well.
Welcome Qwerty
There are several here that fall into the download everything to your Mac camp, and there are others like me who keep everything in the cloud. IMO there are good reasons for both methods.
I have 18+ years of mail in my Google account and never have a problem finding messages when searching in the web client or the Gmail IOS app. My workflow frequently involves linking emails to tasks and notes so it makes sense for me to keep everything in the same place. And this is doubly important because I’m a mobile first user.
Apple has never been know for great search so keeping a copy of your mail in EagleFiler (the app I use for one of my email backups), or Devonthink as recommended by @glenthompson should improve your ability to find messages and files. But I see no reason to remove mail from your account.
To add to my comments, a lot of my opinion comes from my new my wife’sc experiences. Before retirement she was an Exchange admin and I maintained some mission critical systems. She saw the results of people cramming everything into their email accounts and the problems when the store got corrupted. I was involved with disaster recovery testing for said critical systems.
As has been discussed here regarding backups, recovery testing is an important part of your backup strategy. If you keep important information in your email store, have you attempted to recover that data from your backups? If ransomware attacks your imap server, how do you get that back?
Exchange server is a whole different animal. Our old v5.5 used to blow up on a regular basis. I was never a fan of Exchange. I can understand how that experience would make you distrustful of email systems.
I replaced Exchange with a “carrier grade” system from CommuniGate running on Linux initially and later on OSX. And I literally never had another software problem with email for the next 16 years.
“I literally never had another software problem with email for the next 16 years.” That’s what I like to hear 
Thank you WayneG. Spending time trying to fix search, I kept asking myself whether I should have taken a different fork in the road way back and signed up for gmail when it was still invite only. 
Thank you @AlanRalph. I will check out MailMate. Yes, through all of this, I spend a few hours just unsubscribing from email lists, which has helped a lot. Lots of good things said about DEVONthink which I look forward to leaning more about it. But right now baby steps like unsubscribing, creating folders, serve side rules, etc.
Thank you @glenthompson. That is an interesting thought— exporting emails into a document management system. It gets at what I was thinking when I mentioned just downloading all my emails to my Mac and searching them there. I will have to look into EagleFiler and DEVONThink. Yes, you are understanding my problem, when you mention that search can be a problem, and attachments only add to that problems. I lost search but I never even thought about losing all my emails since IMAP is sync not backup. Maybe not the worst thing in the world but I would like to preserve my ability to search through years of old email when I need to. Thanks again!
Although I’ve always maintained folders in email, I recently decided that I was leaving a lot of potentially quite sensitive stuff on the servers of my email platforms, and that I probably ought to be more rigorous in storing stuff robustly. My decision was to create a DevonThink database just for email. I have multiple email addresses and decided to ignore this; instead I file all email by content type (receipt, etc.), which was roughly what my folders were. Once a week I go through my inboxes and move everything to DT. Or delete what isn’t needed - I’ve decided to be much stricter with this (why am I keeping delivery emails once an item is delivered?).
You wouldn’t actually need folders in DT really - in my use case I will always know what I’m looking for, and DT’s search function would suffice. But I like folders.
Having an empty email it turns out is very satisfying, and I only leave bits in there that are pending.
(*NB I’m not referring to work email, which for me I have no legal control over and can’t remove/archive elsewhere.)