issue with email account, inability to receive, and name server

Homestead hosts my website and email accounts.  When an external user sends an email to one of my email accounts, the email bounces with the message "Address not found - Your message wasn't delivered to <email address> because the address couldn't be found, or is unable to receive mail.

My domain is registered at tucows, and whois reports that my name servers are currently set to 
sdn.iecc.com
osdn.iecc.com
light.lightlink.com

One of my nontechnical users contacted homestead yesterday to ask about the problem, and was told that we needed to change our name servers to:
ns1.mdnsservice.com
ns2.mdnsservice.com
ns3.mdnsservice.com

Could someone who is expert in these matters please confirm the above.  Is the correct solution to the problem indeed to change my name servers as described above, why will this solve the problem, will making this change affect my website?  and this is something we do at tucows.com, the place where our domain is registered, right?
thanks so much for all assistance.