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Can custom-domain email have no extra monthly cost?
Sometimes the extra line on this month’s card is $0. The cost of having custom-domain email is not. Those are different questions. This page answers the first one with conditions you can check, and it refuses the second as a slogan.
Nothing here is a measured story about a particular production mailbox. Usage, the Railway invoice, and the date of that usage were not recorded in the repository, so this article does not describe one person’s bill as a case study.
Marginal cost and total cost
Total cost is everything required: the domain renewal, the hosting plan you already pay or would have to start, Resend, backups, and time. Marginal cost is what changes because you added Mailstead.
| You already have | Adding Mailstead changes the monthly card when |
|---|---|
| A domain | It doesn’t, until the year rolls over. Amortize the renewal if you want it in a monthly total. The calculator divides the annual price by 12 |
| Railway Hobby at $5, with unused included usage | Hosting increment is $0 while this service’s measured usage fits in the unused credit. Hobby includes $5 of usage. The credit resets each cycle and does not roll over |
| Nothing on Railway | You pay at least the Hobby fee, $5, even if resource usage is $1 |
| Resend Free, and this month stays within 3,000 emails and 100 on the busiest day | Provider increment is $0. Received mail counts |
| More mail than that | Provider increment is at least the Pro fee, $20 for 50,000 emails |
Sources, checked 2026-10-14: Railway pricing, Resend pricing.
A conditional example, in USD
Assume the workspace already pays for Hobby, $4 of the $5 usage credit is still free, the domain renewal is already paid, backups are left at $0, and the month is 400 messages with no day above 100.
- Standalone total, as if this were the only Railway project: $5.00 hosting plus $0 Resend.
- Incremental total: $0 hosting plus $0 Resend.
The $5 did not disappear. It was already on the invoice. Call the incremental total $0. Do not call email free.
Change one assumption and the zero goes away:
| Change | Incremental provider or host |
|---|---|
| 3,001 messages in the month | Resend Pro at $20. Hosting can still be $0 |
| 101 messages on one day, even if the month is under 3,000 | Free is ineligible. The next included plan in this model is Pro at $20 |
| Usage of $6 and only $4 of credit left | $2 of Railway usage, plus Resend |
| A new Railway account | $5 Hobby minimum, even when usage is inside the credit |
| A domain that costs $18 per year and was not already owned | $1.50 per month if you amortize it. Google, Zoho, and Microsoft need that domain too |
Administration sits outside both totals. An hour spent on DNS is an hour, whether or not the card changed.
What people mean by free, and what fails
Zoho’s free mail plan is $0 for up to five users on one domain in regions where it is offered, with 5 GB per user and without IMAP, POP, or ActiveSync (Zoho pricing). That is a hosted free tier with product limits, not an unused Railway credit. Workspace and Exchange Online Plan 1 do not have a permanent $0 custom-domain tier on the pages checked for the cost guide.
Mailstead will not stay at a $0 provider line if the team’s mail grows. There is no load test that says 50 people fit in Resend Free. Count a month of sent plus received mail before you tell the team there is no extra charge.
The software remains $0 either way. The MIT licence is not a hosting credit.