Twilio SendGrid is a cloud-based email API platform that enables applications to send transactional and marketing emails with high deliverability.

SendGrid offers tiered email API plans with free plan including 100 emails/day. Paid plans include Essentials ($19.95/month), Pro ($89.95/month), and Enterprise with custom pricing. The service provides SMTP and API access, email validation, dedicated IPs (additional $30/month), and overage charges up to $0.00133/email. Additional Email API costs are separate from Marketing Campaigns billing.
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Maildoso is an SMTP and Google Workspace mailbox provider built specifically for cold email senders, offering reliable deliverability with IP rotation across global data centers.
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Postmark is a transactional email API service that helps developers send reliable application emails with high deliverability and comprehensive tracking.