Swap sendgrid by SMTP

[mmabrouk]

We currently use sendgrid for sending emails. Sendgrid provides a general SMTP interface to send emails. We want to migrate towards using this. This would allow self-hosting users to use their SMTP servers instead of being limited to sendgrid.

Goals

• Migrate the code to use SMTP instead of Sendgrid
• Migrate the environment variables to use SMTP
• Keep Sendgrid fallback in case the old env variables are there
• Update the documentation and env.examples with the new data

[linear-code]

AGE-3798

[Shunmuka]

Hi! I’d like to work on this issue.

My plan is to keep the change scoped:

• Add SMTP config in api/oss/src/utils/env.py
• Update email_service.py to use provider order: SMTP first, SendGrid fallback, no-op last
• Keep existing invitation/password-reset call sites unchanged
• Update runtime env derivation so SMTP-only deployments can enable email delivery/email OTP
• Update the env example files
• Run ruff format and ruff check

I’ll keep SMTP enabled detection strict: host + port + sender email, so incomplete SMTP config does not accidentally flip auth to OTP.

[mmabrouk]

This sounds like a plan @Shunmuka!

Please make sure to use the PR template for submission. Please make sure also to test the feature locally and share a video, we unfortunately can't accept external PRs without it.

Let me know if I should assign this issue to you.

[Shunmuka]

Yes I would love to take on this issue! Working on the implementation right now.