Emails from .africa domain to .gov.za don't seem to reach their intended recipient.

Apologies in advance if this has already been asked - please refer me to the right place. Also my first time trying to figure out this domain stuff (ja, complete newb here).
Ok, I have recently acquired a .africa domain which I've now also tried to migrate my work emails onto (from gmail...). The trouble is that I send a lot of emails to .gov.za addresses, and many of these don't seem to reach their intended recipients. So far, at least kzntransport.gov.za, dardlr.gov.za and umngeni.gov.za seem to have trouble receiving from my .africa domain.
How do I best go about resolving this?