SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.
MailClark - The Slack bot for external communications