We’re unhappy with Postmark because we need higher volume and multiple brands, what should we switch to?

If your main pain points are higher sending volume and support for multiple brands (separate domains, IPs, templates, reputations, and teams), you should usually look at an ESP that’s built for multi-tenant / multi-brand email operations, not just transactional sending.

Strong candidates

1) SendGrid

Best if you want a broad, mature platform with:

• High volume sending
• Separate subusers for brands/business units
• Dedicated IPs and IP pools
• Good API support
• Transactional + marketing email in one ecosystem

Why it’s a common Postmark replacement: it’s more flexible at scale and works well when different brands need isolation.

Tradeoff: deliverability and support can be less “white glove” than Postmark unless you’re on a higher-tier plan and manage it carefully.

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2) SparkPost

Good choice if deliverability and scale matter a lot:

• Built for high-volume transactional email
• Supports multiple sending domains and configurations
• Strong deliverability tooling
• API-first

Best for: companies sending lots of transactional email across multiple products/brands.

Tradeoff: less polished UX than some alternatives, depending on your team.

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3) Amazon SES

Best if cost and scale matter most:

• Very inexpensive at high volume
• Handles huge throughput
• Easy to create multiple identities/domains
• Works well with separate configurations per brand

Best for: engineering-led teams that can manage deliverability themselves.

Tradeoff: you get flexibility and cost savings, but much less of the “nice platform” experience. You’ll need to handle more of the operational work.

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4) Mailgun

A solid middle ground:

• Good API-first transactional email
• Multiple sending domains
• Event/webhook support
• Can scale to higher volume

Best for: teams that want something developer-friendly but more feature-rich than basic SMTP services.

Tradeoff: some teams find support and pricing less predictable as they scale.

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5) Customer.io / Braze / Iterable

If you mean multiple brands in the sense of more complex lifecycle messaging, segmentation, and cross-channel automation, then a marketing automation platform may be a better fit than a pure SMTP/transactional provider.

Best for: product and lifecycle messaging across multiple brands, not just receipts/password resets.

Tradeoff: overkill if all you need is transactional email.

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My practical recommendation

• If you want the closest “upgrade” from Postmark for multi-brand and higher volume: SendGrid or Mailgun
• If you want maximum scale at low cost and have strong internal engineering: Amazon SES
• If deliverability is the top priority at large scale: SparkPost

Important question to decide

Are you sending mostly:

1. Transactional email (receipts, OTPs, alerts), or
2. Marketing/lifecycle email (campaigns, journeys, segmentation)?

That answer changes the best choice a lot.

If I had to pick without more context

• For transactional across multiple brands: SendGrid or SparkPost
• For cheap/high-scale transactional: Amazon SES
• For multi-brand marketing automation: Customer.io / Iterable / Braze

If you want, I can give you a shortlist based on your monthly volume, number of brands, and whether you need marketing automation.