I have encountered a strange issue, in certain mailboxes it happens that emails arrive with earlier minutes, for example; I receive an email at 15:30 which I read, then a few minutes later I receive an email at 15:35 which I also read, a few minutes later I receive other emails with a time after 15:36, but there are also unread emails between 15:30-15:35 that were not shown in the mailbox previously.

I have checked the time zone settings, both on the server and on the client, which are correctly configured.

Is anyone else having this problem?

What could be happening?