I've got an e-mail which was actually sent 27 minutes ago. (Zoho mail is slow right now..)

I've got an e-mail which was actually sent 27 minutes ago. (Zoho mail is slow right now..)

Hi. I'm writing this in Seoul, South Korea.
Today I had a problem with zoho mail.
My client said she sent me an e-mail 20 minutes ago.
She captured images for the proof.

But I didn't get the e-mail on time.
I asked her to sent me through other way.

And I got her e-mail after 7 minutes later.

I googled what's the problem, but I only found old complaints.

What's happening on Zoho mail?