As we all know Zoho is currently under heavy DDOS attack https://www.zoho.com/service-updates/blog/zoho-services-under-criminal-attack.html

My question is what happens to mail undelivered during the attack, because I havent't received any email for last 2 days and sender didn't get any "Undelivered mail ..." response. Are these mail lost or will they be delivered later (in next few days)?