one of our clients is using your free zoho mail service with their own domain - targosz-kancelaria.pl

They have noticed multiple issus with gmail e-mails delay up to few hours, especially from gmail

They had as well issue with 17MB attachment not going through

The issue is not related to used mail client - same was observed while using mail.zoho.com

According to them, their client using gmail didn't get any return mail with info about issue and they got to know about the issue via phone.

Are you able to verify that?

Is there any additional info you need me to provide? (if you need to have specific mail title and date to check the particular e-mail - what is the safe way to provide it?)