MailboxManager 4+

Utility to remote-check in one go one or several mailboxes (i.e. mailboxes you access through Emailer applications such as Mail, Thunderbird and the like) and fully manage their messages (inspect, delete, reply etc.) before downloading them. But be aware that:
• @me.com and @icloud adresses are not supported.
• Certified mail is not supported.
• The accounts are accessed one after the other. So if you are looking for an app that will show all the mails of all your accounts in a single list, the app is NOT for you.

Main features:
• Mailbox: it is possible to get the list of all its messages or a selection of them (ex. the last five messages, or messages from 7 to 11); and if you leave copy of them on the server, you can retrieve only the last (new) ones.
• Messages: of each message you can view its partial or full content; and when necessary, you can reply, redirected or forward it. Its attachments too can be inspected and downloaded to disk. Should you find any undesired message, you have the option to mark it as SPAM and to delete it.
• Databases: the SPAM database offers criteria to mark as SPAM incoming messages; while the White List database holds the addresses of friendly mails that --when checking mail-- will be marked as such.
• Import email addresses from Apple Contacts.
• Quitting MailboxManager, your Emailer application can be automatically launched to retrieve the remaining messages.
• Scheduled mail-checking supported. In such case, the application can work in background mode.
• In background mode, the Menubar may show the app icon and the number of messages received.
• gMail/Yahoo etc., 2 Step Verification and App Password supported (see Preferences > Account).