Many common problems with Mail can be fixed, For example:
1. You have a mailbox that shows a number of unread messages in the mailbox list, but when you click on the mailbox there do not seem to be any unread messages inside.
2. Messages seem to have disappeared; they show up when you search your Mac using Spotlight but not when browsing or searching in Mail.
3. A smart mailbox doesn’t seem to be finding the messages that you think it should.
4. You click on a mailbox that you know contains some messages, but Mail doesn’t show any.
5. Messages are colored as spam but remain in the inbox, even though your SpamSieve rule is set to move them to the Spam mailbox.
6. You try to delete messages, but they come back or Mail reports an error.
7. Mail is very slow at browsing or searching messages.
1. Remove the mail cache to speed up mail and release more space.
2. Empty the trash and erase deleted messages in Mail.