Unexpected server response in "DATA_RECEIVED" state

I am sending message requests to an SMTP server and analysing the response from the server.
I have the following setup for **aiosmtpd**.
**server.py**:
```
import asyncio
from aiosmtpd.controller import Controller

class CustomSMTPHandler:

async def handle_DATA(self, server, session, envelope):
print(f"Message from: {envelope.mail_from}")
print(f"Message to: {envelope.rcpt_tos}")
print(f"Message data:\n{envelope.content.decode('utf-8')}")
return '250 OK'

# Run the SMTP server
controller = Controller(CustomSMTPHandler(), hostname='127.0.0.1', port=8025)
controller.start()

print("SMTP server is running on port 8025...")

try:
asyncio.get_event_loop().run_forever()

except KeyboardInterrupt:
controller.stop()
print("SMTP server stopped.")
```
**client.py**:
```
import smtplib
import json
from tqdm import tqdm

def run_smtp_tests(server_address, port, tests_file, output_file):
# Load test cases from the JSON file
with open(tests_file, "r") as f:
test_cases = json.load(f)

results = []

count = 0
# Loop through each test case
for test in tqdm(test_cases):
count += 1
input_seq, state, test_input = test
print(f"Running test {count} for state: {state}, input: {test_input}")
print(f"test case: {test}\n")
total_input_seq = input_seq + [test_input]

try:
# Connect to the SMTP server
server = smtplib.SMTP(server_address, port)

# Execute input sequence to reach the desired state
for input in total_input_seq:
print(f"Input: {input}")
if input == "EHLO":
response = server.ehlo()
elif input == "HELO":
response = server.helo()
elif input == "MAIL FROM:":
response = server.mail("rathin.singha2012@gmail.com")
elif input == "RCPT TO:":
response = server.rcpt("rsingha@cs.ucla.edu")
elif input == "DATA":
response = server.docmd("DATA")
server.send("Hi\r\n.\r\n")
elif input == ".":
server.send("\r\n.\r\n")
response = server.getreply()
elif input == "QUIT":
response = server.quit()
else:
server.send(f"{input}\r\n")
response = server.getreply()

print(f"Response: {response}")

results.append((state, test_input, response))
except Exception as e:
results.append((state, test_input, str(e)))
finally:
# Quit the server connection
try:
server.quit()
except:
pass

# Save results to the output file
with open(output_file, "w") as f:
for result in results:
f.write(f"{result}\n")

# Example Usage
run_smtp_tests(
server_address="127.0.0.1",
port=8025,
tests_file="tests.json",
output_file="results.txt"
)
```
Save the following test case in **tests.json** in the same directory:
```
[
[
[
"HELO",
"MAIL FROM:",
"RCPT TO:",
"DATA"
],
"DATA_RECEIVED",
"."
]
]
```
I get the following responses from the **aiosmtpd** server:
```
Input: HELO
Response: (250, b'rajdeep')
Input: MAIL FROM:
Response: (250, b'OK')
Input: RCPT TO:
Response: (250, b'OK')
Input: DATA
Response: (354, b'End data with .')
Input: .
Response: (250, b'OK')
```

I also ran the test case on **opensmtpd** but got a different set of responses:
```
Input: HELO
Response: (250, b'rajdeep Hello [127.0.1.1] [127.0.0.1], pleased to meet you')
Input: MAIL FROM:
Response: (250, b'2.0.0 Ok')
Input: RCPT TO:
Response: (250, b'2.1.5 Destination address valid: Recipient ok')
Input: DATA
Response: (354, b'Enter mail, end with "." on a line by itself')
Input: .
Response: (550, b'5.7.1 Delivery not authorized, message refused: Message is not RFC 2822 compliant')
```

If you look at the final **opensmtpd** response, it returns an error code 550, but **aiosmtpd** accepts it. Why is there a discrepancy?