Answer
Yes — each attachment on an incoming email is read in as its own separate Application Message, which you can then route to your target BizAPI using standard content-based routing rules configured on the reader, passing the attachment's XML content as the BizAPI's input. If you instead need to read the actual body text of the email, rather than an attachment, enable the 'Parse Body' option on the Mail Reader configuration — but note that email body parsing this way expects the message to be sent as plain text rather than HTML-formatted email, or the body parsing won't work correctly.