Should I mark messages as read if an user replied to it by email?

1. What does mark as read mean in email?
2. What does marking email as unread do?
3. Why are my emails not being marked as read in Outlook?

What does mark as read mean in email?

What does mark emails as read mean? There are two main statuses that you can set on your emails: read and unread. Marking as read simply removes the “unread” notification, even if you haven't actually read the email.

What does marking email as unread do?

If you want to remember to read a message later, you can mark it as unread. You can also mark messages as read without opening them.

Why are my emails not being marked as read in Outlook?

Click File > Options > Advanced. Under Outlook panes, click Reading Pane. Select the Mark items as read when viewed in the Reading Pane check box.