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4 Commits

Author SHA1 Message Date
B. Petersen
9667fe661c make 'experimental' more outstanding 2023-12-12 19:46:26 +01:00
B. Petersen
3141431ee3 use a class for the banner, make sure it is always width of page 2023-12-12 19:39:30 +01:00
B. Petersen
ac2517df4b add domain right of the menu, standardize menu help-code 2023-12-12 19:27:39 +01:00
B. Petersen
f467d7bcd1 move menu up 2023-12-12 18:48:24 +01:00
23 changed files with 101 additions and 218 deletions

View File

@@ -25,56 +25,54 @@ DNS domain name (FQDN), for example `chat.example.org`.
ssh root@CHATMAIL_DOMAIN
```
2. Install the `cmdeploy` command in a virtualenv
2. Install the `cmdeploy` command in a virtualenv
```
git clone https://github.com/deltachat/chatmail
cd chatmail
scripts/initenv.sh
source scripts/initenv.sh
```
3. Create chatmail configuration file `chatmail.ini`:
```
scripts/cmdeploy init CHATMAIL_DOMAIN
cmdeploy init CHATMAIL_DOMAIN
```
4. Deploy to the remote chatmail server:
```
scripts/cmdeploy run
cmdeploy run
```
5. To output a DNS zone file from which you can transfer DNS records
to your DNS provider:
```
scripts/cmdeploy dns
cmdeploy dns
```
6. To check status of your remotely running chatmail service:
```
scripts/cmdeploy status
cmdeploy status
```
7. To test your chatmail service:
```
scripts/cmdeploy test
cmdeploy test
```
8. To benchmark your chatmail service:
```
scripts/cmdeploy bench
cmdeploy bench
```
### Refining the web pages
```
scripts/cmdeploy webdev
cmdeploy webdev
```
This starts a local live development cycle for chatmail Web pages:

View File

@@ -11,15 +11,9 @@ class Config:
self._inipath = inipath
self.mail_domain = params["mail_domain"]
self.max_user_send_per_minute = int(params["max_user_send_per_minute"])
self.max_mailbox_size = params["max_mailbox_size"]
self.delete_mails_after = params["delete_mails_after"]
self.username_min_length = int(params["username_min_length"])
self.username_max_length = int(params["username_max_length"])
self.password_min_length = int(params["password_min_length"])
self.passthrough_senders = params["passthrough_senders"].split()
self.passthrough_recipients = params["passthrough_recipients"].split()
self.filtermail_smtp_port = int(params["filtermail_smtp_port"])
self.postfix_reinject_port = int(params["postfix_reinject_port"])
self.passthrough_recipients = params["passthrough_recipients"].split()
self.privacy_postal = params.get("privacy_postal")
self.privacy_mail = params.get("privacy_mail")
self.privacy_pdo = params.get("privacy_pdo")

View File

@@ -12,7 +12,6 @@ from socketserver import (
import pwd
from .database import Database
from .config import read_config, Config
NOCREATE_FILE = "/etc/chatmail-nocreate"
@@ -23,17 +22,14 @@ def encrypt_password(password: str):
return "{SHA512-CRYPT}" + passhash
def is_allowed_to_create(config: Config, user, cleartext_password) -> bool:
def is_allowed_to_create(user, cleartext_password) -> bool:
"""Return True if user and password are admissable."""
if os.path.exists(NOCREATE_FILE):
logging.warning(f"blocked account creation because {NOCREATE_FILE!r} exists.")
return False
if len(cleartext_password) < config.password_min_length:
logging.warning(
"Password needs to be at least %s characters long",
config.password_min_length,
)
if len(cleartext_password) < 9:
logging.warning("Password needs to be at least 9 characters long")
return False
parts = user.split("@")
@@ -42,17 +38,11 @@ def is_allowed_to_create(config: Config, user, cleartext_password) -> bool:
return False
localpart, domain = parts
if (
len(localpart) > config.username_max_length
or len(localpart) < config.username_min_length
):
logging.warning(
"localpart %s has to be between %s and %s chars long",
localpart,
config.username_min_length,
config.username_max_length,
)
return False
if domain == "nine.testrun.org":
# nine.testrun.org policy, username has to be exactly nine chars
if len(localpart) != 9:
logging.warning(f"localpart {localpart!r} has not exactly nine chars")
return False
return True
@@ -70,7 +60,7 @@ def lookup_userdb(db, user):
return get_user_data(db, user)
def lookup_passdb(db, config: Config, user, cleartext_password):
def lookup_passdb(db, user, cleartext_password):
with db.write_transaction() as conn:
userdata = conn.get_user(user)
if userdata:
@@ -82,7 +72,7 @@ def lookup_passdb(db, config: Config, user, cleartext_password):
userdata["uid"] = "vmail"
userdata["gid"] = "vmail"
return userdata
if not is_allowed_to_create(config, user, cleartext_password):
if not is_allowed_to_create(user, cleartext_password):
return
encrypted_password = encrypt_password(cleartext_password)
@@ -97,7 +87,7 @@ def lookup_passdb(db, config: Config, user, cleartext_password):
)
def handle_dovecot_request(msg, db, config: Config):
def handle_dovecot_request(msg, db, mail_domain):
short_command = msg[0]
if short_command == "L": # LOOKUP
parts = msg[1:].split("\t")
@@ -107,15 +97,15 @@ def handle_dovecot_request(msg, db, config: Config):
res = ""
if namespace == "shared":
if type == "userdb":
if user.endswith(f"@{config.mail_domain}"):
if user.endswith(f"@{mail_domain}"):
res = lookup_userdb(db, user)
if res:
reply_command = "O"
else:
reply_command = "N"
elif type == "passdb":
if user.endswith(f"@{config.mail_domain}"):
res = lookup_passdb(db, config, user, cleartext_password=args[0])
if user.endswith(f"@{mail_domain}"):
res = lookup_passdb(db, user, cleartext_password=args[0])
if res:
reply_command = "O"
else:
@@ -133,7 +123,8 @@ def main():
socket = sys.argv[1]
passwd_entry = pwd.getpwnam(sys.argv[2])
db = Database(sys.argv[3])
config = read_config(sys.argv[4])
with open("/etc/mailname", "r") as fp:
mail_domain = fp.read().strip()
class Handler(StreamRequestHandler):
def handle(self):
@@ -142,7 +133,7 @@ def main():
msg = self.rfile.readline().strip().decode()
if not msg:
break
res = handle_dovecot_request(msg, db, config)
res = handle_dovecot_request(msg, db, mail_domain)
if res:
self.wfile.write(res.encode("ascii"))
self.wfile.flush()

View File

@@ -2,7 +2,7 @@
Description=Chatmail dict authentication proxy for dovecot
[Service]
ExecStart={execpath} /run/dovecot/doveauth.socket vmail /home/vmail/passdb.sqlite {config_path}
ExecStart={execpath} /run/dovecot/doveauth.socket vmail /home/vmail/passdb.sqlite
Restart=always
RestartSec=30

View File

@@ -111,9 +111,6 @@ class BeforeQueueHandler:
if not mail_encrypted and check_mdn(message, envelope):
return
if envelope.mail_from in self.config.passthrough_senders:
return
passthrough_recipients = self.config.passthrough_recipients
envelope_from_domain = from_addr.split("@").pop()
for recipient in envelope.rcpt_tos:

View File

@@ -7,48 +7,18 @@ mail_domain = {mail_domain}
# If you only do private test deploys, you don't need to modify any settings below
#
#
# Account Restrictions
#
# how many mails a user can send out per minute
max_user_send_per_minute = 60
# maximum mailbox size of a chatmail account
max_mailbox_size = 100M
# time after which seen mails are deleted
delete_mails_after = 40d
# minimum length a username must have
username_min_length = 9
# maximum length a username can have
username_max_length = 9
# minimum length a password must have
password_min_length = 9
# list of chatmail accounts which can send outbound un-encrypted mail
passthrough_senders =
# list of e-mail recipients for which to accept outbound un-encrypted mails
passthrough_recipients =
#
# Deployment Details
#
# where the filtermail SMTP service listens
filtermail_smtp_port = 10080
# postfix accepts on the localhost reinject SMTP port
postfix_reinject_port = 10025
#
# Privacy Policy
#
# postal address of privacy contact
privacy_postal =

View File

@@ -1,25 +1,23 @@
#!/usr/local/lib/chatmaild/venv/bin/python3
#!/usr/bin/python3
""" CGI script for creating new accounts. """
import json
import random
from chatmaild.config import read_config, Config
CONFIG_PATH = "/usr/local/lib/chatmaild/chatmail.ini"
mail_domain_path = "/etc/mailname"
def create_newemail_dict(config: Config):
def create_newemail_dict(domain):
alphanumeric = "abcdefghijklmnopqrstuvwxyz1234567890"
user = "".join(random.choices(alphanumeric, k=config.username_min_length))
password = "".join(random.choices(alphanumeric, k=config.password_min_length + 3))
return dict(email=f"{user}@{config.mail_domain}", password=f"{password}")
user = "".join(random.choices(alphanumeric, k=9))
password = "".join(random.choices(alphanumeric, k=12))
return dict(email=f"{user}@{domain}", password=f"{password}")
def print_new_account():
config = read_config(CONFIG_PATH)
creds = create_newemail_dict(config)
domain = open(mail_domain_path).read().strip()
creds = create_newemail_dict(domain=domain)
print("Content-Type: application/json")
print("")

View File

@@ -1,16 +1,17 @@
from chatmaild.config import read_config
def test_read_config_basic(example_config):
assert example_config.mail_domain == "chat.example.org"
assert not example_config.privacy_supervisor and not example_config.privacy_mail
assert not example_config.privacy_pdo and not example_config.privacy_postal
def test_read_config_basic(make_config):
config = make_config("chat.example.org")
assert config.mail_domain == "chat.example.org"
assert not config.privacy_supervisor and not config.privacy_mail
assert not config.privacy_pdo and not config.privacy_postal
inipath = example_config._inipath
inipath = config._inipath
inipath.write_text(inipath.read_text().replace("60", "37"))
example_config = read_config(inipath)
assert example_config.max_user_send_per_minute == 37
assert example_config.mail_domain == "chat.example.org"
config = read_config(inipath)
assert config.max_user_send_per_minute == 37
assert config.mail_domain == "chat.example.org"
def test_read_config_testrun(make_config):
@@ -23,10 +24,4 @@ def test_read_config_testrun(make_config):
assert config.filtermail_smtp_port == 10080
assert config.postfix_reinject_port == 10025
assert config.max_user_send_per_minute == 60
assert config.max_mailbox_size == "100M"
assert config.delete_mails_after == "40d"
assert config.username_min_length == 9
assert config.username_max_length == 9
assert config.password_min_length == 9
assert config.passthrough_recipients == ["privacy@testrun.org"]
assert config.passthrough_senders == []
assert config.passthrough_recipients

View File

@@ -9,35 +9,29 @@ from chatmaild.doveauth import get_user_data, lookup_passdb, handle_dovecot_requ
from chatmaild.database import DBError
def test_basic(db, example_config):
lookup_passdb(db, example_config, "asdf12345@chat.example.org", "q9mr3faue")
data = get_user_data(db, "asdf12345@chat.example.org")
def test_basic(db):
lookup_passdb(db, "link2xt@c1.testrun.org", "Pieg9aeToe3eghuthe5u")
data = get_user_data(db, "link2xt@c1.testrun.org")
assert data
data2 = lookup_passdb(
db, example_config, "asdf12345@chat.example.org", "q9mr3jewvadsfaue"
)
data2 = lookup_passdb(db, "link2xt@c1.testrun.org", "Pieg9aeToe3eghuthe5u")
assert data == data2
def test_dont_overwrite_password_on_wrong_login(db, example_config):
def test_dont_overwrite_password_on_wrong_login(db):
"""Test that logging in with a different password doesn't create a new user"""
res = lookup_passdb(
db, example_config, "newuser12@chat.example.org", "kajdlkajsldk12l3kj1983"
)
res = lookup_passdb(db, "newuser1@something.org", "kajdlkajsldk12l3kj1983")
assert res["password"]
res2 = lookup_passdb(db, example_config, "newuser12@chat.example.org", "kajdslqwe")
res2 = lookup_passdb(db, "newuser1@something.org", "kajdlqweqwe")
# this function always returns a password hash, which is actually compared by dovecot.
assert res["password"] == res2["password"]
def test_nocreate_file(db, monkeypatch, tmpdir, example_config):
def test_nocreate_file(db, monkeypatch, tmpdir):
p = tmpdir.join("nocreate")
p.write("")
monkeypatch.setattr(chatmaild.doveauth, "NOCREATE_FILE", str(p))
lookup_passdb(
db, example_config, "newuser12@chat.example.org", "zequ0Aimuchoodaechik"
)
assert not get_user_data(db, "newuser12@chat.example.org")
lookup_passdb(db, "newuser1@something.org", "zequ0Aimuchoodaechik")
assert not get_user_data(db, "newuser1@something.org")
def test_db_version(db):
@@ -51,21 +45,21 @@ def test_too_high_db_version(db):
db.ensure_tables()
def test_handle_dovecot_request(db, example_config):
def test_handle_dovecot_request(db):
msg = (
"Lshared/passdb/laksjdlaksjdlaksjdlk12j3l1k2j3123/"
"some42123@chat.example.org\tsome42123@chat.example.org"
"some42@c3.testrun.org\tsome42@c3.testrun.org"
)
res = handle_dovecot_request(msg, db, example_config)
res = handle_dovecot_request(msg, db, "c3.testrun.org")
assert res
assert res[0] == "O" and res.endswith("\n")
userdata = json.loads(res[1:].strip())
assert userdata["home"] == "/home/vmail/some42123@chat.example.org"
assert userdata["home"] == "/home/vmail/some42@c3.testrun.org"
assert userdata["uid"] == userdata["gid"] == "vmail"
assert userdata["password"].startswith("{SHA512-CRYPT}")
def test_50_concurrent_lookups_different_accounts(db, gencreds, example_config):
def test_50_concurrent_lookups_different_accounts(db, gencreds):
num_threads = 50
req_per_thread = 5
results = queue.Queue()
@@ -74,7 +68,7 @@ def test_50_concurrent_lookups_different_accounts(db, gencreds, example_config):
for i in range(req_per_thread):
addr, password = gencreds()
try:
lookup_passdb(db, example_config, addr, password)
lookup_passdb(db, addr, password)
except Exception:
results.put(traceback.format_exc())
else:

View File

@@ -127,19 +127,3 @@ def test_excempt_privacy(maildata, gencreds, handler):
content = msg.as_bytes()
assert "500" in handler.check_DATA(envelope=env2)
def test_passthrough_senders(gencreds, handler, maildata):
acc1 = gencreds()[0]
to_addr = "recipient@something.org"
handler.config.passthrough_senders = [acc1]
msg = maildata("plain.eml", acc1, to_addr)
class env:
mail_from = acc1
rcpt_tos = to_addr
content = msg.as_bytes()
# assert that None/no error is returned
assert not handler.check_DATA(envelope=env)

View File

@@ -4,24 +4,26 @@ import chatmaild
from chatmaild.newemail import create_newemail_dict, print_new_account
def test_create_newemail_dict(example_config):
ac1 = create_newemail_dict(example_config)
def test_create_newemail_dict():
ac1 = create_newemail_dict(domain="example.org")
assert "@" in ac1["email"]
assert len(ac1["password"]) >= 10
ac2 = create_newemail_dict(example_config)
ac2 = create_newemail_dict(domain="example.org")
assert ac1["email"] != ac2["email"]
assert ac1["password"] != ac2["password"]
def test_print_new_account(capsys, monkeypatch, maildomain, tmpdir, example_config):
monkeypatch.setattr(chatmaild.newemail, "CONFIG_PATH", str(example_config._inipath))
def test_print_new_account(capsys, monkeypatch, maildomain, tmpdir):
p = tmpdir.join("mailname")
p.write(maildomain)
monkeypatch.setattr(chatmaild.newemail, "mail_domain_path", str(p))
print_new_account()
out, err = capsys.readouterr()
lines = out.split("\n")
assert lines[0] == "Content-Type: application/json"
assert not lines[1]
dic = json.loads(lines[2])
assert dic["email"].endswith(f"@{example_config.mail_domain}")
assert dic["email"].endswith(f"@{maildomain}")
assert len(dic["password"]) >= 10

View File

@@ -243,7 +243,7 @@ def _configure_postfix(config: Config, debug: bool = False) -> bool:
return need_restart
def _configure_dovecot(config: Config, debug: bool = False) -> bool:
def _configure_dovecot(mail_server: str, debug: bool = False) -> bool:
"""Configures Dovecot IMAP server."""
need_restart = False
@@ -253,7 +253,7 @@ def _configure_dovecot(config: Config, debug: bool = False) -> bool:
user="root",
group="root",
mode="644",
config=config,
config={"hostname": mail_server},
debug=debug,
)
need_restart |= main_config.changed
@@ -266,13 +266,14 @@ def _configure_dovecot(config: Config, debug: bool = False) -> bool:
)
need_restart |= auth_config.changed
files.template(
src=importlib.resources.files(__package__).joinpath("dovecot/expunge.cron.j2"),
files.put(
src=importlib.resources.files(__package__)
.joinpath("dovecot/expunge.cron")
.open("rb"),
dest="/etc/cron.d/expunge",
user="root",
group="root",
mode="644",
config=config,
)
# as per https://doc.dovecot.org/configuration_manual/os/
@@ -422,7 +423,7 @@ def deploy_chatmail(mail_domain: str, mail_server: str, dkim_selector: str) -> N
_install_remote_venv_with_chatmaild(config)
debug = False
dovecot_need_restart = _configure_dovecot(config, debug=debug)
dovecot_need_restart = _configure_dovecot(mail_server, debug=debug)
postfix_need_restart = _configure_postfix(config, debug=debug)
opendkim_need_restart = _configure_opendkim(mail_domain, dkim_selector)
mta_sts_need_restart = _install_mta_sts_daemon()

View File

@@ -110,15 +110,6 @@ def status_cmd(args, out):
print(line)
def test_cmd_options(parser):
parser.add_argument(
"--slow",
dest="slow",
action="store_true",
help="also run slow tests",
)
def test_cmd(args, out):
"""Run local and online tests for chatmail deployment.
@@ -130,10 +121,9 @@ def test_cmd(args, out):
out.check_call(f"{sys.executable} -m pip install deltachat")
pytest_path = shutil.which("pytest")
pytest_args = [pytest_path, "cmdeploy/src/", "-n4", "-rs", "-x", "-vrx", "--durations=5"]
if args.slow:
pytest_args.append("--slow")
ret = out.run_ret(pytest_args)
ret = out.run_ret(
[pytest_path, "cmdeploy/src/", "-n4", "-rs", "-x", "-vrx", "--durations=5"]
)
return ret

View File

@@ -86,7 +86,7 @@ plugin {
plugin {
# for now we define static quota-rules for all users
quota = maildir:User quota
quota_rule = *:storage={{ config.max_mailbox_size }}
quota_rule = *:storage=100M
quota_max_mail_size=30M
quota_grace = 0
# quota_over_flag_value = TRUE
@@ -137,8 +137,8 @@ service imap-login {
}
ssl = required
ssl_cert = </var/lib/acme/live/{{ config.mail_domain }}/fullchain
ssl_key = </var/lib/acme/live/{{ config.mail_domain }}/privkey
ssl_cert = </var/lib/acme/live/{{ config.hostname }}/fullchain
ssl_key = </var/lib/acme/live/{{ config.hostname }}/privkey
ssl_dh = </usr/share/dovecot/dh.pem
ssl_min_protocol = TLSv1.2
ssl_prefer_server_ciphers = yes

View File

@@ -0,0 +1,4 @@
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE 40d INBOX
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE 40d Deltachat
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE 40d Trash
2 30 * * * dovecot doveadm purge -A

View File

@@ -1,4 +0,0 @@
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE {{ config.delete_mails_after }} INBOX
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE {{ config.delete_mails_after }} Deltachat
2 0 * * * dovecot doveadm expunge -A SEEN BEFORE {{ config.delete_mails_after }} Trash
2 30 * * * dovecot doveadm purge -A

View File

@@ -1,16 +1,6 @@
import requests
from cmdeploy.genqr import gen_qr_png_data
def test_gen_qr_png_data(maildomain):
data = gen_qr_png_data(maildomain)
assert data
def test_fastcgi_working(maildomain, chatmail_config):
url = f"https://{maildomain}/cgi-bin/newemail.py"
print(url)
res = requests.post(url)
assert maildomain in res.json().get("email")
assert len(res.json().get("password")) > chatmail_config.password_min_length

View File

@@ -43,18 +43,18 @@ def test_reject_forged_from(cmsetup, maildata, gencreds, lp, forgeaddr):
@pytest.mark.slow
def test_exceed_rate_limit(cmsetup, gencreds, maildata, chatmail_config):
def test_exceed_rate_limit(cmsetup, gencreds, maildata):
"""Test that the per-account send-mail limit is exceeded."""
user1, user2 = cmsetup.gen_users(2)
mail = maildata(
"encrypted.eml", from_addr=user1.addr, to_addr=user2.addr
).as_string()
for i in range(chatmail_config.max_user_send_per_minute + 5):
for i in range(100):
print("Sending mail", str(i))
try:
user1.smtp.sendmail(user1.addr, [user2.addr], mail)
except smtplib.SMTPException as e:
if i < chatmail_config.max_user_send_per_minute:
if i < 60:
pytest.fail(f"rate limit was exceeded too early with msg {i}")
outcome = e.recipients[user2.addr]
assert outcome[0] == 450

View File

@@ -1,5 +1,4 @@
import time
import re
import random
import pytest
@@ -21,24 +20,14 @@ class TestEndToEndDeltaChat:
assert msg2.text == "message0"
@pytest.mark.slow
def test_exceed_quota(self, cmfactory, lp, tmpdir, remote, chatmail_config):
def test_exceed_quota(self, cmfactory, lp, tmpdir, remote):
"""This is a very slow test as it needs to upload >100MB of mail data
before quota is exceeded, and thus depends on the speed of the upload.
"""
ac1, ac2 = cmfactory.get_online_accounts(2)
chat = cmfactory.get_accepted_chat(ac1, ac2)
def parse_size_limit(limit: str) -> int:
"""Parse a size limit and return the number of bytes as integer.
Example input: 100M, 2.4T, 500 K
"""
units = {"B": 1, "K": 2**10, "M": 2**20, "G": 2**30, "T": 2**40}
size = re.sub(r'([KMGT])', r' \1', limit.upper())
number, unit = [string.strip() for string in size.split()]
return int(float(number) * units[unit])
quota = parse_size_limit(chatmail_config.max_mailbox_size)
quota = 1024 * 1024 * 100
attachsize = 1 * 1024 * 1024
num_to_send = quota // attachsize + 2
lp.sec(f"ac1: send {num_to_send} large files to ac2")

View File

@@ -228,25 +228,18 @@ def imap_or_smtp(request):
@pytest.fixture
def gencreds(chatmail_config):
def gencreds(maildomain):
count = itertools.count()
next(count)
def gen(domain=None):
domain = domain if domain else chatmail_config.mail_domain
domain = domain if domain else maildomain
while 1:
num = next(count)
alphanumeric = "abcdefghijklmnopqrstuvwxyz1234567890"
user = "".join(
random.choices(alphanumeric, k=chatmail_config.username_max_length)
)
if domain == "nine.testrun.org":
user = f"ac{num}_{user}"[:9]
else:
user = f"ac{num}_{user}"[: chatmail_config.username_max_length]
password = "".join(
random.choices(alphanumeric, k=chatmail_config.password_min_length)
)
user = "".join(random.choices(alphanumeric, k=10))
user = f"ac{num}_{user}"[:9]
password = "".join(random.choices(alphanumeric, k=12))
yield f"{user}@{domain}", f"{password}"
return lambda domain=None: next(gen(domain))

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@@ -1,6 +0,0 @@
#!/usr/bin/env bash
#
# Wrapper for cmdelpoy to run it in activated virtualenv.
set -e
. venv/bin/activate
cmdeploy "$@"

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@@ -4,3 +4,6 @@ python3 -m venv venv
venv/bin/pip install -e chatmaild
venv/bin/pip install -e cmdeploy
source venv/bin/activate
echo activated 'venv' python virtualenv environment containing "cmdeploy" tool

View File

@@ -26,7 +26,7 @@ The first login sets your password.
- You may send up to 60 messages per minute
- Seen messages are removed 40 days after arriving on the server
- Messages are unconditionally removed 40 days after arriving on the server
- You can store up to [100MB messages on the server](https://delta.chat/en/help#what-happens-if-i-turn-on-delete-old-messages-from-server)