Message size exceeds capabilities of MX responsible for the recipient

Message size exceeds capabilities of MX responsible for the recipient

Hello,
I have a problem with my Zoho email address. I host my domain externally at Namecheap. When I send files to my email address I get the following error: "Message size exceeds capabilities of MX responsible for the recipient". Now the question is it because I don't have an upgrade at the moment? Or is it a general problem that cannot be solved with an upgrade. Thanks for your answers in advance!