fastapi-mail: send_message as background task is not working

Mails are not going out in background.

We have backgrounds tasks working well in other endpoints. Any idea of what could be the issue?

We tried without a template (exactly like your example) and it does not work either.

class SigninEmailSchema(BaseModel):
    recipient: EmailStr
    a: str
    b: str


@router.post('/email/signin')
async def send_signin_email(
        bg: BackgroundTasks,
        contents: SigninEmailSchema,
    ) -> JSONResponse:

    message = MessageSchema(
        subject = ' subject ',
        recipients = [contents.recipient],
        template_body = {
            'a': contents.a,
            'b': contents.b,
        },
    )

    fm = FastMail(conf)

    #await fm.send_message(message, template_name='signin.html') # WORKS
    bg.add_task(fm.send_message, message, template_name='signin.html') # DOES NOT WORK

    return JSONResponse(
        status_code=200,
        content = {'message': 'email was sent'},
)