I made a SmartMailbox "Today" to have in it all the mails I receive daily on my 4 different mail accounts. It works OK, but next day, all "yesterday" mails disappear, giving place to the new "today" ones! Where can I find the "yesterdays" mails?

Flacano,

It would depend on how you have your mailboxes set up with your accounts or if you have any mail rules applied to send them elsewhere. This could either be in your corresponding inbox for those accounts or archived.

Use rules to manage emails you receive in Mail on Mac

The best thing to do is check all your mailboxes to be sure where they are going or check the webmail of your accounts to see where the mail is heading when not being sorted into the the Smart Mailbox.

Take care.

Hello Flacano,

Welcome to the Apple Support Communities. From your post, there seems to be some mail not in a Smart Mailbox you created.

It appears the Smart Mailbox is working as you made it. Yesterdays mail would go into either an inbox or archive depending on how your mail accounts are set up. Today means only the current day, meaning all mail that came on in that specific day, not a 24-hour period: Use Smart Mailboxes in Mail on Mac

Best regards.