kitio.aiOpenAI Codex vs Mails.ai
A side-by-side look at pricing plans, free tiers, features, pros and cons, updated for 2026. OpenAI Codex has the lower starting price: about $8 a month, against $20 for Mails.ai.
At a glance
Best for
Pricing model
Starting price
Free plan
Made by
Based in
Rating
Key features
- Cloud coding tasks
- Codex CLI
- IDE extension
- Desktop app
- Automatic PR review
- Inbox per agent through one API call
- TypeScript and Python SDKs
- MCP server
- Injection scan on inbound mail
- Send from your own domain
| Feature | OpenAI Codex | Mails.ai |
|---|---|---|
| Best for | OpenAI's coding agent in the cloud, CLI, IDE and desktop app | Email API that gives AI agents their own inboxes |
| Category | Coding | Coding |
| Pricing model | Freemium | Freemium |
| Starting price | $8/mo | $20/mo |
| Free plan | Yes | Yes |
| Made by | OpenAI | Mails.ai |
| Based in | United States | – |
| Rating | No ratings yet | No ratings yet |
| Key features |
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Pricing compared
OpenAI Codex has the lower starting price: about $8 a month, against $20 for Mails.ai.
Free plan
Cheapest paid plan
Top plan
Free trial
6 plans
Free
Free
- Limited Codex usage
- Via ChatGPT account
Go
$8/mo
- ChatGPT Go plan
- More Codex usage than Free
Plus
$20/mo
- ChatGPT Plus plan
- Codex in CLI, IDE and cloud
Pro
$100/mo
- Starting price; $200 and $500 tiers
- Highest Codex limits
Business
$25/mo
- Per user
- Shared workspace and admin controls
Enterprise
Contact sales
- Enterprise security
- Flexible usage
3 plans
Free
Free
- 3,000 emails per month
- 3,000 inbound replies per month
- 1 agent
Pro
$20/mo
- 50K emails per month
- 5 agents
- Send from your own domain
- Signed webhooks
Scale
$99/mo
- 250K emails per month
- Unlimited agents
- Per-agent allowlists and send limits
Prices in USD, checked Oct 28, 2026 or later. Plans change often, so confirm on each tool's site before you buy.
Pros and cons
OpenAI Codex
- Included in ChatGPT plans
- Runs many tasks in parallel
- Open-source CLI
- Token-based limits are hard to predict
- Free tier usage is small
Mails.ai
- Free tier with no card
- Controls on who an agent can email
- Works with major coding agents
- Free plan allows just 1 agent
- Custom domains need Pro
- Dedicated IP is on request only
Which one should you choose?
Choose OpenAI Codex if you want:
- Included in ChatGPT plans
- Runs many tasks in parallel
- Open-source CLI
Watch out: token-based limits are hard to predict.
Choose Mails.ai if you want:
- Free tier with no card
- Controls on who an agent can email
- Works with major coding agents
Watch out: free plan allows just 1 agent.
OpenAI Codex vs Mails.ai FAQ
What is the difference between OpenAI Codex and Mails.ai?
OpenAI Codex: OpenAI's coding agent in the cloud, CLI, IDE and desktop app. Mails.ai: Email API that gives AI agents their own inboxes. Both are coding tools.
Is OpenAI Codex or Mails.ai cheaper?
OpenAI Codex has the lower starting price: about $8 a month, against $20 for Mails.ai.
Do OpenAI Codex and Mails.ai have free plans?
OpenAI Codex: Yes. Mails.ai: Yes.
Who makes OpenAI Codex?
OpenAI Codex is made by OpenAI, based in United States.
Who makes Mails.ai?
Mails.ai is made by Mails.ai.
Which should I choose, OpenAI Codex or Mails.ai?
Choose OpenAI Codex if you value included in chatgpt plans and runs many tasks in parallel. Choose Mails.ai if you value free tier with no card and controls on who an agent can email.