Seeking an Email Platform for High-Volume Sending (3M+ Emails/Month) for Our Lawn Care SaaS

I’m looking for advice on choosing an email platform that fits our specific use case. We run a SaaS CRM for a trade group (lawn care/landscaping). Our users are landscapers, and each landscaper has their own clients (homeowners). Through our platform, landscapers create job schedules and charge their clients, and our CRM sends automated emails on their behalf. These emails include job notifications, thank-you emails after jobs, and pending invoice reminders. Here’s our situation:

• We currently have hundreds of landscaper users, with a growth trajectory that could hit thousands in the next few years.
• On average, we send about 100 emails per day per landscaper. For example, with 1,000 landscapers, that’s 100,000 emails/day or roughly 3 million emails/month.
• We’re currently using Zoho Mail, but we’re hitting their outgoing email limits fast, and it’s not scaling with our growth.
• All emails are sent from a single domain (e.g., [[email protected]](mailto:[email protected])) as part of our automation feature—no need for multiple domains.
• We don’t need the email platform to manage contacts (our in-house admin site handles that). We just need a robust system for sending large volumes of emails reliably.

We’re looking for a platform that:

• Can handle high-volume sending (millions of emails/month) without throttling or strict limits.
• Supports sending from a single domain.
• Focuses on transactional emails (job notifications, invoices, etc.) rather than marketing-heavy features we won’t use.
• Scales cost-effectively as our user base grows.

Any recommendations for platforms that fit this use case? We’ve heard about options like SendGrid, Mailerlite, Amazon SES, or Postmark, but I’d love to hear your experiences—especially if you’ve dealt with similar volumes or automation needs. How do they handle deliverability, pricing, and integration for a setup like ours?