using Zoho business on with info@muvipromo.it (domain verified), I can only send but not receive emails. On the settings panel, both incoming and outgoing emails seem to be active.
I have changed the MX settings with my current provider, setting the IP to 72.5.230.114 (as found this thread: https://help.zoho.com/portal/en/community/topic/problems-with-zoho-mail-6-12-2009). My provider only allows numerical IP addresses in the MX register settings. The MX redirect was confirmed as active by my provider.
However emails get bounced back with the following message:
550 RCPT TO:<info@muvipromo.it> Relaying not allowed - please use SMTP AUTH [RCPT_TO]