Send reply-to param in airflow emailoperator - airflow

Question

I am sending mail using airflow emailOperator. Is there any way to send "reply-to" parameter also. i tried default_param={'key':'value'} but throwing exception as invalid parameter.
I read this https://github.com/apache/airflow/blob/main/airflow/operators/email.py
https://github.com/apache/airflow/blob/main/tests/operators/test_email.py
But I don't know where i am doing mistake.
version : 2.0.2
email_op = EmailOperator(
task_id='send_email',
to=destination['emails'],
subject=destination['subject'],
html_content=destination['message'],
files=[file.name],
default_param={'Reply-To': 'reply_to#example.com'},
)
email_op.execute(context)

Answer 1

It would be passed via dictionary custom_headers, as per the Official Source Code and Official Docs
I actually took the Reply-To directly from the official Airflow unit test.
There was a bug patched in release 2.3.0 with the send_email function to correctly pass the custom_headers. This might be your root cause...
Here is the link to the issue
Here is the pull request to resolve it
For new comers here is how you would send the custom_headers when using 2.3.0 and above.
from airflow.operators.email_operator import EmailOperator
t1 = EmailOperator(
task_id='send_email',
to="email#example.com",
subject="Airflow Example",
html_content=""" <h3>Email Test</h3> """,
cc="email#example",
custom_headers = {
'Reply-To': 'reply_to#example.com'
}
)