We already require that outgoing connections
use STARTTLS so other servers need a valid TLS
certificate to accept messages from us.
It is then very unlikely that they cannot use TLS
to send messages to us.
Conversely, if they only can send messages to use without TLS,
it likely does not have STARTLS on its port 25
and then we don't want to accept messages from them
because we will likely not be able to reply.
Stalwart sends `NOTIFY=DELAY,FAILURE`
to request Delivery Status Notifications.
aiosmtpd does not support any parameters,
not just ORCPT, so we have to ignore all of them.
High-security mode could be configured
to handle more connections by increasing process_limit,
but has problems logging in many users at once after
each Dovecot restart or config reload.
Otherwise email providers which allow to bring your own domain
and use the same IP addresses for all customers
send wildcard certificate instead of the correct one
and Postfix refuses to connect with an error
server certificate verification failed for example.org[A.B.C.D]:25: num=62:hostname mismatch
It does not work because of `smtpd_proxy_filter`
forwarding the message to filtermail
and we cleanup the message once
filtermail reinjects it on port 10025.
I tested with -tls1_2 option
of openssl s_client
that TLS 1.2 connections
are no longer possible
on any ports except port 25.
Port 25 requires at least TLS 1.2
for encrypted connections.
`authclean` cleanup server is used by
reinjecting smtpd running on localhost:10025 by default.
It runs after filtermail
and currently removes `Received` header
to avoid leaking IP address.
Can as well be used to replace `Subject` lines
with `Subject: [...]`.
If there are multiple `Subject` lines,
all of them should be replaced.
This allows us to avoid dealing with
localized subjects, including SecureJoin
messages `vc-request` and `vg-request`
which can have Subject lines like
Subject: =?utf-8?q?Nachricht_von_nrn178fi4=40nine=2Etestrun=2Eorg?=
Replace \r\r\n in literal.eml test with \r\n
to make `test_filtermail_no_literal_packets`
actually reach `check_openpgp_payload()`
and make `check_openpgp_payload()` more strict.
unbound-control is not installed out of the box
and even once installed `flush_zone` does not seem
to work reliably.
Instead of trying to flush the cache from unbound,
we now query authoritative nameserver directly using `dig`.
perform_initial_checks may exit early
and not add `acme_account_url` if required DNS
records are not found.
In this case other `cmdeploy run` fails
with KeyError.
To avoid this, `acme_account_url` should always be set.
Unlike DNS checks, running acmetool
may not fail due to network errors,
so it is more reliable and should be checked first.
I wanted to add `COMPRESS=DEFLATE`,
but it should be added only for sessions
that are logged in because `COMPRESS`
command does not work before logging in.
Dovecot already does it correctly
if we don't overwrite the capability string.
DictProxy can have transactions with the same name
(most frequently `1`) processed in parallel.
Dovecot expects that transaction names on each connection
are independent.
Otherwise nginx fails when user actually tries to connect,
logs have errors such as
`invalid port in upstream "127.0.0.1:imaps"`
and
`invalid port in upstream "127.0.0.1:submissions"`.
Services are distinguished based on ALPN.
For example,
openssl s_client -connect example.org:443 -alpn smtp
gives SMTP connection and
openssl s_client -connect example.org:443 -alpn imap
gives IMAP connection.
Oversigning (including header name in DKIM-Signature
more times that it appears in the mail) prevents
adding more headers with the same name
without invalidating DKIM signature.
We don't want middleboxes to insert a second From header,
adding Cc field to mails that don't have one etc.
LMTP does not deduplicate messages
if sieve plugin is used.
We don't check for Auto-Submitted header anymore
as iOS application has a notification service
and should not display "You have a new message".
Ensure that first part only contains "Version: 1"
and second part only contains base64 payload
enclosed in "-----BEGIN PGP MESSAGE-----"
and "-----END PGP MESSAGE-----".
link2xt
