Blocking mails from server form?

Blocking mails from server form?

Dear Zoho team,
I have following question: Is there any kind of blocking of mails sent from server (via code, not from specific client)?

On my pages I have a form, which when properly filled should send email to my mailbox. This works properly with my another mailbox on seznam.cz, but not with my mailbox on Zoho ( yourway@smallstonepath.info). The reason could be that in the "From" field I set non-existing address (because I just need to get information about filled form, not to answer). Receiving emails from existing addresses via standard clients is working normally.

So, when I try to send email to my Zoho mailbox via my asp.net form, I get en error
System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.1.1 Sorry, no mailbox here by that name.

I was searching a solution for two hours but found nothing.
Thanks in advance!

Best regards
Petr