Newton Mail - Newton is a fully featured mail client available for Android, iOS, macOS and Windows.
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
Aqua Mail - Android Mail Client.
Mailwasher - Over 8 million people use MailWasher as their spam filter
Gmail - Gmail is available across all your devices Android, iOS, and desktop devices. Sort, collaborate or call a friend without leaving your inbox.
SpamAssassin - Use this program to "Unspam" your mailbox(es).