OpenAI API vs Mailgun
Frontier models: GPT-5, o-series reasoning, image, audio, embeddings
vs. Email API for developers with deep deliverability tooling
Pricing tiers
OpenAI API
Free Tier (Trial)
$5 free credit for new accounts. Rate-limited.
Free
Pay-as-you-go
No monthly min. Per-token pricing by model.
$0 base (usage-based)
Usage Tiers (1-5)
Automatic tier promotion based on cumulative spend. Higher tiers = higher rate limits + new model access.
$0 base (usage-based)
Enterprise
Custom. Priority access, SLA, dedicated capacity.
Custom
Mailgun
Free
100 emails/day. 1 custom domain, 1-day log retention, 1 inbound route. No credit card.
Free
Basic
$15/month. 10,000 emails/month, no daily limit, 5 inbound routes.
$15/mo
Foundation
$35/month (1st month free). 50,000 emails/month, 1,000 custom domains, 5-day retention.
$35/mo
Scale
$90/month. 100,000 emails/month, SAML SSO, 5,000 email validations, dedicated IP pools, 30-day retention.
$90/mo
Enterprise
Custom. Deliverability services, managed onboarding.
Custom
Free-tier quotas head-to-head
Comparing free-tier on OpenAI API vs free on Mailgun.
| Metric | OpenAI API | Mailgun |
|---|---|---|
| No overlapping quota metrics for these tiers. | ||
Features
OpenAI API · 12 features
- Assistants API — Stateful assistants with tools, threads, file search.
- Batch API — 50% discount for async processing within 24h.
- Chat Completions API — Classic /v1/chat/completions endpoint.
- Files API — Upload docs for retrieval, fine-tuning, batch.
- Fine-Tuning — Supervised + DPO fine-tuning for GPT-4o, GPT-4.1, GPT-4o-mini.
- Function Calling — JSON-schema tool calling; parallel calls supported.
- Moderation — Safety classifier API (free).
- Prompt Caching — Auto-cache repeated prefixes; 50% cheaper cached hits.
- Realtime API — WebSocket streaming voice + text with low latency.
- Responses API — Stateful conversational API.
- Structured Outputs — Enforced JSON schema compliance.
- Vision — Image input for GPT models.
Mailgun · 14 features
- Batch Sending — Send up to 1,000 recipients per API call via recipient variables.
- Dedicated IPs — IP pools with auto warmup. Scale+ tier.
- Deliverability Suite — Inbox placement testing, DMARC reporting, seed lists.
- Email Logs — Searchable log of all send attempts + events.
- Email Templates — Template builder + variables + versioning.
- Email Validation — Real-time email verification (syntax, MX, role accounts, disposable).
- EU Region — Data stored in EU for GDPR-sensitive customers.
- Inbound Routing — Route incoming emails to URLs/SMTP. Attachment forwarding.
- Mailing Lists — Unlimited mailing lists with bulk subscribe/unsubscribe.
- Open/Click Tracking — HTML + text tracking with configurable tracking domain.
- SAML SSO — Scale+ tier.
- Send API — REST/SMTP send with MIME + tracking.
- Tags — Tag messages to slice stats.
- Webhook Events — delivered, opened, clicked, unsubscribed, complained, permanent_fail, temporary_…
Developer interfaces
| Kind | OpenAI API | Mailgun |
|---|---|---|
| SDK | openai-dotnet, openai-go, openai-node, openai-python | mailgun.js (Node), mailgun-php, mailgun-python, mailgun-ruby |
| REST | OpenAI REST API | Mailgun REST API |
| MCP | OpenAI MCP | — |
| OTHER | Realtime API (WebSocket) | Inbound Routing, SMTP Relay, Webhooks |
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