email forwarding works but a user doesn't exist error returned to sender

[dgrun]

I have email set up to forward from an address at one domain to another: d@solverworld.com forwards to d@chainwave.com.  I do not want a mailbox at solverworld.  This forwarding works (I get emails at chainwave.com) but the sender gets an error response to their email:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  d@solverworld.com
    LMTP error after RCPT TO:<d@solverworld.com>:
    550 5.1.1 <d@solverworld.com> User doesn't exist:
    d@solverworld.com

 I have tried both a default address at solverworld for unrouted email of both 'error response' and 'discard', but the same thing happens in each case.

[CG]

Hey @dgrun,

First let me say welcome to the community!

Generally this sort of error often appears in one of two instances. The first, the sender may have misspelled the address they're sending to but you still received it because of a "catch-all" setting on the domain. The other is that your domain may not be using the proper MX records to appear like a valid email address to send to. 

In case of the latter,  you can confirm your correct MX records the domain should be pointed to here. Let us know if this helps. 

[dgrun]

Thanks.  I can look at my MX records, but not sure what they are supposed to be.

Should it point to smtp.secureserver.net or something else?