It appears that any email sent from 'full PAYH' domains to 'preview PAYH' domains is dumped with no bounceback. Full PAYH qmail tries to deliver such mail locally (within the full PAYH environment) but cannot of course do so.
PAYH CS have been trying to get to the bottom of this problem (first manifested as redirected
email being dumped) for some time with no success (vide my previous posts). Yesterday PAYH CS pinpointed 'preview PAYH' recipient domains as the likely problem. I have tested this proposal by sending an email to a preview PAYH domain and a non-preview domain. It arrives at the latter but not the former.
I still need a solution, but - if the above conclusion is correct - it might explain some other users 'vanishing mail' problems as well.
[Mods: I have raised this as a separate post as it may be highly significant to many 'preview PAYH' users]
Zen from May 17. PN Business account from 2004 - 2017