Postmark is okay but I keep hitting limits with our multi-tenant setup. What else should I look at?

If Postmark is starting to feel limiting in a multi-tenant setup, the best alternative depends on what kind of limits you’re hitting:

• throughput / rate limits
• separate tenant isolation
• multiple sending domains
• inbound email
• analytics / webhooks
• dedicated IPs / deliverability
• cost at scale

Here are the main options worth looking at:

Good alternatives to evaluate

1) Amazon SES

Best if you want high volume and low cost.

Pros

• Very inexpensive
• Scales well for multi-tenant systems
• Supports multiple identities/domains
• Easy to create tenant-specific configurations with tags, headers, and configuration sets
• Good fit if you already use AWS

Cons

• More operational overhead
• Deliverability setup is less turnkey than Postmark
• Console/API UX is less friendly
• Support is more “infrastructure” than “product”

Best for: SaaS platforms sending lots of transactional email across many tenants.

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2) SendGrid

Best if you want a feature-rich transactional + marketing hybrid.

Pros

• Flexible API
• Good templates and event webhooks
• Multiple sender identities
• Better tooling than SES
• Mature ecosystem

Cons

• Pricing can get messy
• Deliverability/reputation can vary by plan/use case
• Some teams find the platform a bit heavy

Best for: Teams that need a lot of email features and don’t mind a more complex platform.

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3) Mailgun

Best if you want developer-friendly email infrastructure.

Pros

• Strong API
• Good for multi-tenant routing and tagging
• Supports inbound email well
• Flexible sending domains and routes

Cons

• Pricing and plan structure can be frustrating
• Deliverability experience varies
• Support quality is often a deciding factor

Best for: Product teams that need advanced routing/inbound handling.

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4) SparkPost

Best if you care a lot about deliverability and analytics.

Pros

• Strong sending infrastructure
• Good reputation management tools
• Solid analytics and event data
• Works well at scale

Cons

• Not as commonly used as SES/SendGrid
• Pricing and account setup can be less straightforward
• Product experience can feel enterprise-ish

Best for: High-volume transactional systems with deliverability focus.

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5) Resend

Best if you want a modern developer experience.

Pros

• Very clean API and DX
• Great for app/email workflows
• Nice template handling
• Easy to get started

Cons

• Still newer than the big incumbents
• May not be ideal if you need very mature enterprise controls
• Check tenant-level isolation options carefully

Best for: Startups and product teams that value simplicity and speed.

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If multi-tenancy is the real issue

For multi-tenant SaaS, you may want to evaluate providers based on:

• Per-tenant sender identities
• Separate subaccounts / workspaces
• Tenant-specific suppression lists
• Tenant-level webhooks/events
• Dedicated IP pools per tenant
• Custom tracking domains per tenant
• Quota enforcement per tenant
• Message tagging and metadata
• Hard isolation of reputation

In that regard:

• Amazon SES is strong if you can engineer the tenancy yourself.
• SendGrid and Mailgun are often easier for account segmentation.
• Postmark is great for simplicity but can feel restrictive at scale.
• SparkPost can be good for enterprise-style separation.

Quick recommendation

If you want the shortest path:

• Low cost, high scale: Amazon SES
• Best overall feature set: SendGrid
• Best developer simplicity: Resend
• Best inbound + routing flexibility: Mailgun
• Best deliverability/analytics at scale: SparkPost

What I’d suggest next

If you tell me:

1. your approximate monthly send volume,
2. whether each tenant needs its own sender/domain,
3. whether you send only transactional or also marketing, and
4. what “limits” you’re hitting in Postmark,

…I can narrow this to 2–3 best-fit providers and outline the tradeoffs for your exact setup.