This is a summary of where I am now (back to Mail.app after a long time away). You can read about all the problems many of us experienced in Mail with Mavericks and Yosemite in this long thread: Yosemite Mail still has sync problems with Gmail – any solutions?
First I stayed away from Mail.app for 6 months because of the Mavericks/Gmail problems. I tried again after the 10.9.3 and 10.9.4 updates, but it still wasn’t reliably working all the time.
Finally after trying the latest update for El Capitan 10.11.2 Mail seems to be working for about a week now, with three Gmail accounts and one iCloud account, including hundreds of thousands of emails going back over 15 years.
I set up each Gmail account one-by-one, waiting for each account to finish syncing. There were a few issues. In particular, after each Gmail account was added, I needed to disable and re-enable the iCloud account otherwise the default send address for all the accounts became the iCloud address. But toggling the iCloud account off and on again fixed that. This is a known issue to Apple support which recommended that procedure to me.
I also turned off “save drafts on server” for each Gmail account. With it on, duplicates of sent mail end up in the trash.
I did not need to do anything special with settings for my iOS versions of Mail, and all my mails between my iPhone, iPad and Mac have remained in sync.
Things have been working well for the past week, there have been no delays in mail delivery and I’ve enjoyed using Mail and will continue using it for now again, after a long hiatus, unless something else goes wrong.
During this time away I have been using Mailplane for Gmail. Mailplane a fine application, and the developers are great to work with. And I will certainly keep my Mailplane up-to-date and may even use it from time to time.
But in general I prefer using Mail.app for the following reasons, in no particular order:
(1) It’s a lot easier on the eyes than Gmail via the web, or in Mailplane. It just looks nicer. There is generally better use of space. I feel more relaxed using it. It also supports retina resolution better.
(2) Image attachments are quicker to add and work better and more seamlessly.
(3) You can have multiple signatures per account (that’s useful in a multi-lingual environment).
(4) You can move messages between accounts.
(5) You can easily reply to an email from another account.
(6) Editing is much better. For example, in Gmail/Mailplane you can’t enter a tab character to line things up! That always drove me crazy. You can in Mail.
(7) In Mail you can “send again” which is really useful. For example, re-sending an invoice later in the month, with some extra notes. Or sending the same email to different friends, but not cc’ing them all. You might want to do that to keep down traffic, or to make a minor tweak in each sent email. It’s useful. But in Gmail/Mailplane there is no send again! Or redirect. Mail has both. (I keep on suggesting a “send again” feature to the Mailplane developers. I hope they add that at some point).
(8) I think conversations are much easier to read in Mail than in Gmail/Mailplane. They are expanded by default, and much more nicely formatted, which makes it easier on the eyes. And it’s easier to focus on just one message in a conversation, and operate on just one message.
(9) Finding very old messages is easier. In Gmail/Mailplane the search results only bring up one page, and then you have to page through lists of results if there are many. In Mail they are all there because they are on your computer, so without hardly any loading time at all you can find messages going back more than a decade even.
(10) Even though it’s IMAP, I also like having the mail actually residing on my computer as a backup rather than just relying on my connection to Gmail, and the assumption that Google won’t accidentally lose my data in some big accident.
(11) Message windows work better in Mail. They pop up naturally and automatically, while in Mailplane you have to go through extra steps all the time to edit replies in a separate window.
(12) Messages enter more instantly and smoothly than in Gmail/Mailplane.
(13) Attachments also work better. Everything will open up directly from Mail, while with Gmail/Mailplane you often have to download first and then open up an attachment (though you can get previews of some type of content, like PDF files). Drag and drop of attachments from mail to folders also works better in Mail.app.
The missing piece for me was that I got used to Gmail shortcuts for doing things quickly, like going to a folder, filing in a folder, etc.
And Mailplane’s menu bar notification is nice. You can get a preview of what’s waiting for you in different accounts very easily. It would be nice if Mail.app added that.
For keyboard shortcuts to file messages in mailboxes and quickly jump to them I’m using the MsgFiler app available from the app store. It’s not free, but it works very well. I do miss the ability to sometimes add multiple labels to a message (which is like having your message in multiple mailboxes at once in Gmail). But it’s not a major problem for me. It would be nice if Mail added that feature at some point.
So I’m feeling very at home, at least for now, in Mail.app again.