E-mails were coming too slowly.

E-mails were coming too slowly.

Hi, I applied to the Zoho Free business mail and have finished setting few hours ago.

I sent e-mails to my business mail, on average it arrived in three hours. but these were sent quickly. 

Is there a problem on the my e-mail setting? Is it because of FreePlan? Or is the Zoho mail this always slow? 

Please let me know. Thank you.