CampaignKit - Email Validation for marketers. Detect invalid and malicious email addresses in your email lists.
HubSpot - Grow Better With HubSpot: Software that's powerful, not overpowering. Seamlessly connect your data, teams, and customers on one CRM platform that grows with your business.
Sender Policy Framework - This is a diagnostic tool that acts as a Sender Policy Framework (SPF) record lookup
Marketo - Marketo's powerful marketing automation software helps marketers master the art & science of digital marketing to engage customers and prospects.
MailRefine - Decrease Email Bouncing With Best Email Verifier
MailChimp - MailChimp is the best way to design, send, and share email newsletters.