runtime.smtp_blocked

Outgoing mail on port <port> is blocked

A mevcore app hosting error at the “start / health check” stage.

What it means

SMTP ports 25, 465 and 587 are closed on Mevcore to protect against spam.

The build passed, but the app did not start or did not answer the health check.

Typical causes

The app does not listen on 0.0.0.0 and the port from the PORT variable
An environment variable is missing, or the database or Redis is not connected
The start command is wrong or the process exits right away

How to fix it on mevcore

Send mail through the HTTP API of your email provider over port 443: Resend, SendGrid, Mailgun, Postmark and others have libraries for every language. If you need SMTP, write to support.

1 Open the app in the mevcore panel: the Problems card on the overview shows this error and the log line it was found in.
2 After the fix, deploy again. If it fails again, the log ends with [mevcore] lines naming the new error code.
3 The "Ask AI" button next to the error prepares a request for ChatGPT or Claude: the error code, the end of the log without secrets and the app settings.

For an AI assistant

The same in English: paste it together with the log into the AI chat.

mevcore error code: runtime.smtp_blocked
phase: start / health check
diagnosis: Outgoing mail on port <port> is blocked
platform hint: SMTP ports 25, 465 and 587 are closed on Mevcore to protect against spam. Send mail through the HTTP API of your email provider over port 443: Resend, SendGrid, Mailgun, Postmark and others have libraries for every language. If you need SMTP, write to support.
platform docs: https://mevcore.com/llms-full.txt

Related errors

runtime.rails_blocked_host Rails blocks the host <host>

All error codes · How to prepare your project for mevcore · llms-full.txt

Can't fix it?

Message support with the error code: we will tell you what to change in the project or settings.

App hosting