[Bug]: Calcom resend SMTP connection timed out

[racso-dev]

Error Message and Logs

When deploying Calcom through available services, I use resend smtp configuration (a valid one, I tested it on other apps and it works just fine) and when Calcom tries to send emails the connection to resend's smtp server times out and therefore no email of any kind can be sent.

Here are my env variables set in configuration of the services :

[email protected]
NEXT_PUBLIC_WEBAPP_URL=https://calendar.tendiz.ai
[email protected]
EMAIL_SERVER_HOST=smtp.resend.com
EMAIL_SERVER_PASSWORD=some_secret_env_var
EMAIL_SERVER_PORT=465
EMAIL_SERVER_USER=resend
POSTGRES_DB=calendso
SERVICE_BASE64_CALCOMKEY=some_secret_env_var
SERVICE_BASE64_CALCOMSECRET=some_secret_env_var
SERVICE_FQDN_CALCOM=https://calendar.tendiz.ai
SERVICE_PASSWORD_POSTGRES=some_secret_env_var
ALLOWED_HOSTNAMES=tendiz.ai
SERVICE_USER_POSTGRES=some_secret_env_var

(The domain is verified on resend)

Here are some logs of an attempt to send an email :

2025-02-06T23:08:00.385171783Z @calcom/web:start: sendEmail from: [email protected] <[email protected]> subject: 30 Min Meeting between Oscar Rénier and Oscar Rénier Error: Connection timeout
2025-02-06T23:08:00.385181451Z @calcom/web:start:     at SMTPConnection._formatError (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:787:19)
2025-02-06T23:08:00.385190068Z @calcom/web:start:     at SMTPConnection._onError (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:773:20)
2025-02-06T23:08:00.385198624Z @calcom/web:start:     at Timeout.<anonymous> (/calcom/node_modules/nodemailer/lib/smtp-connection/index.js:232:22)
2025-02-06T23:08:00.385207621Z @calcom/web:start:     at listOnTimeout (node:internal/timers:569:17)
2025-02-06T23:08:00.385216036Z @calcom/web:start:     at process.processTimers (node:internal/timers:512:7) {
2025-02-06T23:08:00.385224432Z @calcom/web:start:   code: 'ETIMEDOUT',
2025-02-06T23:08:00.385232697Z @calcom/web:start:   command: 'CONN'
2025-02-06T23:08:00.385240972Z @calcom/web:start: }

Check that little video if you wanna see the problem "live".
Video (I trimed the video because It took around 2 minutes to timeout)

If you have any ideas on how to troubleshoot that issue I'd truly appreciate It.
Thanks in advance for those reading my post hope someone can help.

Steps to Reproduce

1. Go on resend.com create an account and an api key (it's free)
2. Deploy Calcom through Coolify services one click deployment configuring SMTP env variables with resend configuration
3. Trigger a mail by reserving a slot on any event type of your choice

Example Repository URL

No response

Coolify Version

v4.0.0-beta.394

Are you using Coolify Cloud?

No (self-hosted)

Operating System and Version (self-hosted)

Ubuntu 24.04

Additional Information

No response