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552 5.3.4 - Message too big for system

To ensure the best sending rate for our customers and to accommodate for message rules in place by some ISPs, we limit the maximum total size of any message sent to 40MB or less.

Internet mail protocols are not designed as a file transfer protocol, and with many ISPs the maximum message size with attachments that they will allow to be sent to their users is 25MB or less. We recommend that any large transfers be sent via other methods, such as FTP/SFTP, or one of the various secure file sharing services that are available on the internet. There is no way to change this limit.