Source: Any > Destination: G Suite or Exchange/Office 365
When migrating mail into G Suite / Office 365, the error message "Message is too large and attachments cannot be removed" may be returned for some items on import. It occurs when a mail item exceeds the default 50MB size limit in Gmail and Office 365.
You can edit the Max Message Size in the Destination Platform Migration Settings accordingly (this is available as Message size is customizable in Exchange). It is, by default, set to 20971520 bytes, so provided the Exchange server allows message sizes of the same size that you set, it will then be possible to import them without error.
G Suite destinations:
The Gmail API now supports emails up to a max size of 50MB. If the message itself (not including attachments) is larger than 50MB, these messages cannot be imported to Gmail.