Thank you for your post, welcome to the Community Forums!
I'm sorry to hear you're having trouble receiving emails from your friend. Are you able to send emails to them without any errors?
Does the email that your friend is trying to send to you have any attachments? I'd recommend asking them to try changing the contents of the email or just to send a test email with little text on it and no attachments to see if the error persists.
Let us know,