The total size of attachments sent to support, e.g., screenshots, must be limited to less than 5 megabytes in size.
As an example, a user may submit 3 attachments of 1 megabytes each in the same email, but may not submit 3 attachments of 2 megs each in the same email. This is because the latter example totals 6 megabytes in attachments, which is over our 5 megabytes limit.
Also note that some email clients may attach more information to the file(s) you are attaching. As a result, you may reach this 5 megabyte limit than more quickly than you expect.