Mail Drop and iCloud attachments: 20 MB, 5 GB, and where it breaks
The exact figures, the four reasons Mail Drop fails, and what to do beyond 5 GB.
The short answer. iCloud Mail caps the whole message at 20 MB. Above that, Mail Drop takes over: 5 GB per attachment, available for 30 days, out of a 1 TB allowance that does not touch your iCloud storage.
If Mail Drop is not offered to you, or if the send fails, the next section gives the four possible causes.
The exact figures
| What is limited | Value |
|---|---|
| iCloud Mail message, attachments included | 20 MB |
| File size actually accepted as an attachment | ≈ 15 MB |
| Attachment sent via Mail Drop | 5 GB |
| Availability period | 30 days |
| Mail Drop allowance | 1 TB, outside iCloud storage |
Every file type is accepted, and the recipient needs neither a Mac nor an Apple account: they receive an ordinary download link.
The four reasons Mail Drop fails
- The file is over 5 GB. That is a hard ceiling, per attachment. An hour of rushes passes it easily.
- You are not in the Mail app. Mail Drop works from Mail on Mac, iPhone and iPad, and from iCloud.com. From a third-party client or another webmail linked to your iCloud address, it does not exist: you hit the 20 MB wall.
- The 1 TB allowance is full. It frees up as previous sends expire, not on demand.
- The 30 days have run out. The link is then dead, with no warning to the recipient — who writes to tell you “it doesn't work”.
Why a file smaller than the limit gets refused
This is the point the official help pages skip over, and it is almost always the explanation. An email can only carry text. A file — video, photo, PDF, archive — therefore has to be converted into printable characters before it leaves: that is base64 encoding, which writes three bytes as four characters. The file grows by about 33 % in transit.
In other words: to fit inside a 25 MB limit, your file must not exceed about 18 MB on disk. For a 20 MB limit, count on 15 MB. And that limit applies to the whole message — the text, your signature, the inline images and every attachment added together, not just the file you have dragged in.
One last factor, this one invisible: the lower of the two limits decides, yours when sending and the recipient's when receiving. A corporate server often caps at 10 MB. Your message leaves, appears to be sent, and then a non-delivery report comes back an hour later.
The 30-day trap
Mail Drop is made for a quick exchange, not for archiving. Thirty days feel comfortable right up to the moment the recipient opens the email on their return from holiday. No notification warns that a link is nearing its end, and nothing can be extended: everything has to be sent again.
Beyond 5 GB
This is the limit everyone working with images on a Mac runs into: a shoot card, a Final Cut project, a series of RAW files pass 5 GB without effort.
toobigtoshare accepts up to 2 TB, four hundred times the Mail Drop ceiling. You drop the file from your browser, you get a link, you paste it into your message. The recipient clicks and downloads, with no Apple account and no app to install. $5.49 per send, and the file is deleted after 3 days — the deadline is clear, nobody discovers a dead link a month later.
Send the file with toobigtoshare — up to 2 TB, no account, a link to paste into your email.
Frequently asked questions
What is the iCloud Mail attachment limit?
20 MB for the whole message, both sending and receiving. Above that, Mail Drop takes over and accepts up to 5 GB per attachment.
How long does a file sent through Mail Drop stay available?
30 days. After that the link stops working and the file has to be sent again. It is the most common cause of a dead Mail Drop link.
Does Mail Drop use up my iCloud storage?
No. Mail Drop attachments are not counted against your iCloud storage. They have their own 1 TB allowance, shared across all your sends in progress.
How do I send a file over 5 GB from a Mac?
Mail Drop cannot: 5 GB is a hard ceiling per attachment. You have to go through a transfer service and paste the link into the message — toobigtoshare accepts up to 2 TB.
Got a file of several gigabytes to send?
toobigtoshare carries up to 2 TB. No account to create, neither for you nor for the person receiving: you get a link, you paste it into your email. $5.49 per send, file deleted after 3 days.