A network-based solution for automatically processing large email attachments or other files during migration between email platforms or other platforms, as may be embodied by various systems, methods, and non-transitory computer-readable storage media, may involve downloading mailboxes from a source email platform and inspecting the mailboxes for emails containing attachment files. The solution may involve determining a file size of any detected attachment, comparing the file size of the detected attachment file to a predetermined attachment size limit, and uploading a copy of the detected attachment to a storage server for storage when the comparison determines that the file size of the detected attachment file exceeds the predetermined attachment size limit. The solution may further include modifying the email by replacing the detected attachment with a link to the copy of the detected attachment stored at the storage server and then migrating the modified email to the target email platform.