Mail app is using 10GB on my laptop (High Sierra 10.13.3). I don't use it at all; I usually use the web interface and occasionally Thunderbird for my Gmail account.

This is the only Mail-connected account in Internet Accounts. If I were to uncheck it in Internet Accounts for my Gmail account so that I can delete the cache and free up some space, is there the possibility of any unintended consequences? For example, will I somehow stop getting email reminders of things in my BusyCal calendar? Or some other possibility that I am unaware of?

  • Why don't you just try for a day or two?
    – nohillside
    Mar 25 '18 at 14:05
  • I’m with @patrix - make a back up of your Mac (you need that anyhow) and then try it out. : - )
    – bmike
    Mar 25 '18 at 14:09

It is safe to remove your Gmail account from Mail.app without any unintended consequences, as all the Gmail data is stored on Google's servers.

Also, there’s no harm in never setting up any mail account in Mail.app for macOS. The system does want to have a default mail app, so if you click a mailto://hi@me.com link, it will open Mail.app. Mail will then try to onboard a new account, but you can end that action easily by not choosing to continue.

Simply removing a Gmail account from Mail.app won't delete any of your Gmail data (although performing any action on any of the mail or folder will reflect the changes in Gmail). This is the same for any purely cloud based IMAP mail services (iCloud as well as Gmail) where deleting the local cache leaves the server copies of all mail intact.

The only small caution is if you save mails locally and delete a copy from the server - maybe make a quick backup of your Mac or export your local mails to an export file or folder just in case you fear you’ll delete those and want them back.

  • Thank you! My question was more about unintended consequences in the functioning of OSX, by removing the only Mail-connected account in Internet Accounts. Do you know if that could cause a problem?
    – richardmtl
    Mar 25 '18 at 14:03
  • There should be nothing which should stop you from receiving BusyCal email reminders. The only consequence in macOS of removing an email account from Mail.app would be that you will no longer receive new email notifications in the Notification Centre.
    – Nimesh Neema
    Mar 25 '18 at 14:09
  • @richardmtl I can edit that part in to this good answer. No problems - we have dozens of machines with no mail accounts.
    – bmike
    Mar 25 '18 at 14:09

I think it's easiest to keep Mail.app functional and instead reduce the amount of space it uses - mainly by limiting how much mail will be available locally (this is set in gmail).

Note this WILL affect thunderbird as well. Assuming you're using thunderbird for reading new mail, and the web for searching old mail, this works well.

  1. IMAP Limit: gmail.com → Settings → Forwarding and POP/IMAP → Enable IMAP → Folder Size Limits (bottom): Limit IMAP folders... 1000 (or lower).

  2. Don't download attachments automatically: Mail → Settings → Accounts → (choose gmail account) → "Download Attachments": None

You may want to un-sync gmail and make sure all the mail is deleted before re-adding it, if you don't see the space come back (may work on its own if patient).

Also you should periodically clean your large attachments, try searching "size:25000000" in gmail to find and delete the ones you don't need. If you do above, it won't matter much but still good practice.

More info on reducing Mail.app space usage.

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