Repl. It Smtplib Oserror: [Errno 99] Cannot Assign Requested Address

I am trying to run simple emailsender.py script on repl.it to send an email. It works without any problem when I try to run it on desktop PC, but on repl.it I am having an error message OSError: [Errno 99] Cannot assign requested address as detailed below. The emailsender.py program looks like this:

import smtplib

def send_email(username: str, key: str):
    reciever = username+"@theirmail.cz"
    sender = "[email protected]"
    topic = "Autothorization bot"
    
    # header
    msg = "From: %s\r\nSubject: %s\r\nTo: %s\r\n\r\n" % (sender, topic, reciever)

    # add message content
    content = "Your key is: " + key
    msg += content

    server = smtplib.SMTP('smtp.seznam.cz')
    server.login('[email protected]', "my_email_password") 
    server.sendmail(sender, reciever, msg)
    server.quit()

When I try to run the script via python on repl.it, I get this error message after some time:

>>> import emailsender
>>> emailsender.send_email("username", "test_message")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/runner/botpy/emailsender.py", line 24, in send_email
    server = smtplib.SMTP('smtp.seznam.cz')
  File "/usr/lib/python3.8/smtplib.py", line 253, in __init__
    (code, msg) = self.connect(host, port)
  File "/usr/lib/python3.8/smtplib.py", line 337, in connect
    self.sock = self._get_socket(host, port, self.timeout)
  File "/usr/lib/python3.8/smtplib.py", line 308, in _get_socket
    return socket.create_connection((host, port), timeout,
  File "/usr/lib/python3.8/socket.py", line 808, in create_connection
    raise err
  File "/usr/lib/python3.8/socket.py", line 796, in create_connection
    sock.connect(sa)
OSError: [Errno 99] Cannot assign requested address

This .py script is a piece of larger discord.py bot that I am trying to host on repl.it, but this should not have any effect, because this script alone is running well individually on desktop PC.

I've tried my best to figure out the cause of this error, but with no success so far.