Almost all email systems have restrictions on the size of emails that can be sent through the system, and this also applies to Kundo Mail. The limits are set by the third-party systems we use to receive and send mail, so neither of them is unfortunately possible for us to raise.
The limit for all content in outgoing emails (incl. Attachments) is 24 MB. There is also a limit of 17 MB for individual attachments in outgoing emails.
If you try to send an email that is larger than that limit, or attach a file that is larger, you will receive an error message directly in Kundo.
The limit for incoming emails is 40 MB. Individual attachments in incoming emails have no limit but only the limit of 40 MB for the entire email applies.