I'm now using zoho for more than 6 months.

Great soft and all, really fine to tune.

I have the "professional" version.

My team and I use Zoho to send some emails (no mass emailing or emailing campaign, just one mail some times) 

BUT

I can't be sure the mail was sent.

Why I'm asking myself this question? Because sometimes I  Copie Carbone Invisible myself and I don't receive any email... even when I check into my SPAM folder.

So, HOW CAN I BE SURE MY EMAILS ARE SENT ?

This is supposed to be a business app, if my clients don't receive my emails, how am I suppose to make business with them?

Thank you for your help :)

Hugo