We use Google Apps and with users approaching 250K email messages and over 25GB of storage Mail App is getting ever slower for most users.

Are there any guidelines on how large we should let the mailboxes grow?

I have not been able to find any information on limits (even from user experience) online.

3 Answers 3


The Limit is not something programmed into Mail.

In effect, your Hard-Drive storage and the Performance of your Mac are the only limiting factors, not some count of messages in terms of size or number.
As you already noticed, the app gets really slow with Mails over 100k or even 200k on current hardware (perhaps except the Mac Pro).

It is not recommended having such a big MailBox at all.

How I think it should/could be handled :

  • Don't go beyond 10k Mails (in your main Postbox)
  • Move Old Mails into a Mail-Archive

    • Having your own Server for that helps a lot.
      I use a OS X (Mail-) Server with a Roundcube Frontend and a MySQL Database.
      In our company we have a Linux Mail-Server and a Roundcube Frontend with a MySQL DB.

    • The Server can handle those Mails a lot better than Apple Mail. Also roundcube as a Frontend is much faster when going through severel houndred of thousands of mails.

  • If you're reaching a Mail-Count of more than 200k, you are probably collecting a decade of mails (unless you are writing a lot).

  • After 3-5 Years you should store those mails on a Backup Server (Maybe at a different location), safe for nobody to access and safe regarding any kind of loss.

  • There is no mail limit a contrario to Outlook Database (PST). because Mail.app stores all messages individually as separate files. Which is great to avoid data corruption but hell with search indexes creation with big mailboxes (probably the why your Macs are becoming slow)... As said consider archiving on a centralised (Mac) Server (will allow you search by content on mounted shares). If you've updated your Macs lately delete Enveloppe indexes to allow the indexation to complete : support.apple.com/kb/PH14876 to force re-indexing mdimport -r /System/Library/Spotlight/Mail.mdimporter
    – llange
    Commented Jun 1, 2014 at 7:26

The limit is only what your gmail (Google) account gives you.

In my case I have 2 gmail accounts each with 16 Gig Quota Limits- those are standard gmail accounts. You can have more space with gmail account by converting it to premium (pay for it).

Apple Mail limit is your disk space.

Folder limit is none (as many as you like)

If you right click on you gmail account in Apple mail and ask for Account information you will get the limit information you have with the gmail on they server. (not on your Mac).

It looks like this on my mac for one of the accounts:


To monitor what is slowing your Apple Mail down open the Activity under Window Tab in Mail. That one will show you exactly what is going on and who or what is slow.

The Activity window looks something like this:

activity window

Now to your Problem:

Gmail allows you to set limits for how many emails are transferred and synchronized each time you connect.

You can set the number of emails in gmail to speed things up.

I assume you do not need to have all 250000 emails synchronized each time.

Setting the limit will not delete the emails, they are still on your gmail account, the limit is for how many emails are transfered to your Apple Mail and you can set it from 1000 to 10000.

Here is how to:

Limit IMAP

Be aware that if you set it to "Do not limit the number..." that can lead to slowdown:

no limit

Finlay, I would say you do not need to start to deal with your own email server, simple adjustments to Google preferences can provide you with all your needs, but if you need to Google offers a high traffic business solutions as well.


Our Google apps business account has a limit of 30 GB per mailbox by default. Using too many labels/folders can become a bottleneck when syncing but there is actually a bandwidth limit that Apple Mail tends to exceed daily: https://support.google.com/a/answer/1071518

Some recommending settings for Apple Mail (and others) can be found here: https://support.google.com/mail/answer/78892

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