As per Tetsujin's suggestion in the comments I did some further testing.
There seems to be a problem with iCloud and sending a zip file of a folder with a certain amount of files. There appears to be a limit of 127 files in 1 folder, regardless of file type (tried
When sending the mail using the Mail app I get a
message size violation error and the mail can not be sent. Using the iCloud web interface the mail does appear to be sent (no error, appears in 'sent' list) but it never arrives.
Does anyone know why this limit exists? (as Tetsujin mentioned in the comments it might be some 7-bit shenanigans)
If I try to send an email with a 1.3 MB zip file as attachment I get a
message size violation error:
File sizes of the zip file and original folder (1.3 MB and 10.7 MB respectively):
At first I thought it was somehow related the original folder being more than 10 MB, but according to Apple's iCloud support page the limit is 20 MB:
Limits on sending messages
There are several safeguards in place to make sure that only iCloud members can send messages using iCloud. One of these safeguards includes reasonable limits on:
- The size of incoming and outgoing messages (20 MB, up to 5 GB with Mail Drop turned on)
Why am I unable to send this zip file? (also: shouldn't Mail Drop kick in if it thinks the attachment is too large? It is turned on.)