As I understand it, the streaming attachments feature was added to provide a faster option for downloading large attachments.

Is performance also a problem when sending new mail with large attachments? If so, is there a more efficient/faster way to stream attachments UP to the POA?

Or do we still just need to base64-encode the attachment and put it in an attachmentItemInfo object in the message, and send/create via sendItemRequest and/or createItemRequest?