You’re right — in the Automations UI the “Send a notification” action only supports the predefined notification providers. Custom SMTP isn’t available there today. Good news: you can still do this in Prefect 3.x by triggering a small “notify” flow from an Automation, and that flow can send email via any SMTP server using the prefect-email integration. Here are two workable patterns: 1) Recommended: Automation runs a deployment that sends the email via your SMTP - Install the integration:

pip install prefect-email

- Create and save SMTP credentials as a block:

from prefect_email import EmailServerCredentials, SMTPType

creds = EmailServerCredentials(
    username="smtp-user",
    password="your-password",           # will be stored as a SecretStr
    smtp_server="<http://smtp.yourcompany.com|smtp.yourcompany.com>", # your SMTP host
    smtp_type=SMTPType.TLS,             # or SMTPType.SSL
    smtp_port=587,                      # match your server
    verify=True,
)
creds.save("corp-smtp", overwrite=True)

- Create a tiny flow that sends the email:

from prefect import flow
from prefect_email import email_send_message, EmailServerCredentials

@flow(name="send-email-notification")
def notify(subject: str, body: str, to: list[str], email_from: str | None = None):
    creds = EmailServerCredentials.load("corp-smtp")
    email_send_message(
        subject=subject,
        msg=body,
        email_server_credentials=creds,
        email_from=email_from,
        email_to=to,
    )

- Deploy this flow (e.g., with

prefect deploy

from your project). - Create an Automation: - Trigger: When a flow run enters state Failed or Crashed - Action: Run a deployment (select your notify deployment) - Parameters (use templates so the email contains details about the failing run): - subject (template):

[{{ flow_run.state_type }}] {{ flow_run.name }}

- body (template):

Flow: {{ flow.name }}
      Deployment: {{ deployment.name }}
      Run: {{ flow_run.name }} ({{ flow_run.id }})
      State: {{ flow_run.state_type }} - {{ flow_run.state.message }}
      Start: {{ flow_run.start_time }}
      Tags: {{ flow_run.tags }}

- to: e.g.

["<mailto:oncall@yourcompany.com|oncall@yourcompany.com>"]

- email_from: e.g.

<mailto:alerts@yourcompany.com|alerts@yourcompany.com>

Docs: - prefect-email integration - Using templates in Automations - Automation triggers and events 2) Alternative: Call a webhook action If you already have an HTTP endpoint that sends email via your SMTP (e.g., an internal service), you can use the “Call a webhook” action in Automations and template the payload with

{{ flow_run... }}

data. This avoids running a flow but requires an HTTP service you control. To directly answer your observation: the built-in “Send a notification” action is limited to predefined providers. For custom SMTP, trigger a flow (option 1) or call your own webhook (option 2). Would you like me to draft the exact Automation parameters or a sample deployment command based on your repo structure and work pool name?

@Marvin The notification flow is running perfectly but the email is not send, is there something to await ?

Short answer: you don’t need to await anything for the email to send. In Prefect 3.x, calling the

email_send_message

task inside a flow will schedule and run it; the flow will wait for child tasks to finish before completing. If the flow run shows “successful” but you didn’t get an email, it’s almost always configuration or environment. Here’s a quick checklist to pinpoint the issue: - Did the

email_send_message

task actually run and succeed? - In the flow run page, look for a green task run named

email_send_message

. If it’s missing or failed, the logs will explain why. - Ensure required fields are set explicitly: - `email_to`: string or list of strings (e.g.,

"<mailto:oncall@yourcompany.com|oncall@yourcompany.com>"

or

["<mailto:oncall@yourcompany.com|oncall@yourcompany.com>"]

) - `email_from`: many SMTP servers require a valid sender that’s allowed (often must match the authenticated user/domain) - Verify SMTP settings match your server: - STARTTLS: use

SMTPType.TLS

and port 587 - Implicit TLS: use

SMTPType.SSL

and port 465 - Example:

from prefect_email import EmailServerCredentials, SMTPType
    creds = EmailServerCredentials(
        username="smtp-user",
        password="your-password",
        smtp_server="<http://smtp.yourcompany.com|smtp.yourcompany.com>",
        smtp_type=SMTPType.TLS,  # or SMTPType.SSL
        smtp_port=587,
    )

- Corporate/self-signed certs: if you’re on a custom SMTP with a self-signed cert, a quick test is:

creds = EmailServerCredentials(..., verify=False)

If that works, you have a certificate trust issue to fix properly. - Network egress: make sure your worker environment can reach the SMTP host/port (no firewall/security group blocks). - Automation parameters: if you’re templating values, confirm they aren’t empty at runtime. - For example, ensure

to

resolves to a real address: -

["<mailto:oncall@yourcompany.com|oncall@yourcompany.com>"]

- And

subject/body

templates don’t error. Minimal working example inside a flow (explicit arguments):

from prefect import flow
from prefect_email import email_send_message, EmailServerCredentials, SMTPType

@flow
def test_email():
    creds = EmailServerCredentials(
        username="smtp-user",
        password="your-password",
        smtp_server="<http://smtp.yourcompany.com|smtp.yourcompany.com>",
        smtp_type=SMTPType.TLS,
        smtp_port=587,
    )
    email_send_message(
        subject="Test from Prefect",
        msg="This is a test.",
        email_server_credentials=creds,
        email_from="<mailto:alerts@yourcompany.com|alerts@yourcompany.com>",
        email_to=["<mailto:oncall@yourcompany.com|oncall@yourcompany.com>"],
    )

if __name__ == "__main__":
    test_email()

If this test flow’s

email_send_message

task shows success but no email arrives: - Check your SMTP server logs for rejections (e.g., 550/553 sender/recipient issues) - Try using

email_from

= the SMTP username or an allowed sender in that domain If you can share: - the snippet that calls

email_send_message

- your EmailServerCredentials settings (redact secrets) - the task run logs and the Automation parameters …I can help spot the exact culprit quickly. Docs: - prefect-email integration - Using templates in Automations