Reader Joshua Snider seeks more information about one of Yosemite's new Mail features. He writes:

I've heard that I can send really large attachments through Yosemite's Mail, but does that mean that whoever receives my messages has to also be running Yosemite and using Mail as their email client?

No. The Mail Drop feature isn't really using attachments in the way that you're accustomed to. Rather it's using an attachment analogy so that typical users don't have to be confounded by talk of cloud intermediaries.

What Mail Drop does is something akin to you uploading a large file to a cloud service, creating a link to it, and then sending that link to a recipient who can then click on the link and download your file. While this may be what's going on in the background, Apple hides it from you. Instead, if the recipient is running Yosemite on their Mac and using Mail, your file appears to them as an attachment, even though it wasn't sent through your ISP's email gateway.

The one hint you'll see when attaching a large file is a warning that the attachment may be too large to send. Within this warning sheet you're given the options to cancel, try sending it in email regardless of what Mail tells you, or use Mail Drop.

When you send one of these Mail Drop "attachments" to someone who is using an older version of the Mac OS, employs an email client other than Mail, or who works with a Windows PC, they'll receive your message with an embedded link. When they click that link, their default web browser will open and they'll be taken to a website where they can download the file. In this way it's much like sending someone a link from a service such as Dropbox, Google Drive, OneDrive, or Box.com.

Note that Mail Drop/iCloud Mail have certain "fine print" limitations. They include:

  • You must have your iCloud account activated on your Mac and you must send these messages via your iCloud account.
  • A single message can't be larger than 5GB (this includes the message body and any attachments).
  • You can't send an uncompressed folder that contains files. Instead, compress the folder by Control-clicking (right-clicking) on it in the Finder and choosing Compress.
  • You can't send more than 200 messages each day.
  • You can't send messages to more than 1,000 recipients each day from your iCloud account.
  • A single message sent via iCloud can't have more than 100 recipients.
  • You can't store more than 1TB of messages. Attachments expire after 30 days, so as they disappear, space will be freed up.
  • This 30 day limit means your recipients must retrieve these messages within that period of time.

Most people are going to have no problem with these limitations. I think it's a great feature and you likely will as well.