I have a number of POP3 Email Accounts set up in Zoho for separate businesses I run. The idea was when I send out an email it is sen as coming from that email address and NOT my ZOHO email address.
I have had several people reply to emails I have sent them and see in the header of my email the zoho email address is shown and it says some like on behalf of
uuuu@xxxx.com when the latter is my POP3 email.
Have also seen the same thing with some emails that have bounced back to me.