Use of Sieve with Dovecot not possible cause of error

**What happened?** The description of the problem concerns the Thunderbird but also the stand alone version and other sieve editors. I would like to edit Sieve via the plugin/program. My mail account works without problems and can also send/receive. Creating a new account is possible without any problems. As soon as I click on "Connect", the loading bar is permanently there and nothing happens. I have activated debugging in the settings, but I don't know where it is saved. if someone tells me, I can submit the required log later.

**Settings**

Settings from Sieve:

 Server imap.xxxxxx.eu: 4190 (Secured connection) Username

my@fancydomain.eu

**Logs**

dovecot-mailcow_1 | May 9 02:47:16 04888203e1b5 dovecot:  
managesieve-login: Disconnected (no auth attempts in 0 secs): 
user=<>, rip=92.123.123.123, lip=123.123.123.123, TLS 
handshaking: SSL_accept() failed: error:14094412:SSL 
routines:ssl3_read_bytes:sslv3 alert bad certificate: SSL alert 
number 42

**What i tried?**

gnutls-cli --starttls -p 4190 imap.xxxxxx.eu

Output:

`Processed 129 CA certificate(s).

Resolving "imap.xxxxxxxxx.eu:4190"... Connecting to "2a03:4000:34:522:981b:xxxx:xxxx:xxxx:4190"... Simple Client Mode: "IMPLEMENTATION" "Dovecot Pigeonhole" "SIEVE" "fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext vacation-seconds editheader imapflags notify imapsieve vnd.dovecot.imapsieve" "NOTIFY" "mailto" "SASL" "" "STARTTLS" "VERSION" "1.0" OK "Dovecot ready."`

telnet xxx.xxx.xxx.xxx 4190

output:

Connected to xxx.xxx.xxx.xxx.
Escape character is "^]".
"IMPLEMENTATION" "Dovecot Pigeonhole"
"SIEVE" "fileinto reject envelope encoded-character vacation subaddress 
comparator-i;ascii-numeric relational regex imap4flags copy include

variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext vacation-seconds editheader imapflags notify imapsieve vnd.dovecot.imapsieve"

"NOTIFY" "mailto"
"SASL" ""
"STARTTLS"
"VERSION" "1.0"
OK "Dovecot ready."

Added in dovecot.conf in "service managesieve-login" "ssl = no" and after that "ssl = true" but also not working.

dovecot config:

service managesieve-login {
inet_listener sieve {
port = 4190
ssl = no
}
inet_listener sieve_haproxy {
port = 14190
haproxy = yes
}
service_count = 1
process_min_avail = 2
vsz_limit = 1G
}

**OS/Software Informations** Client Thunderbird:

OS: Windows 10
Sieve Version: 0.5.3
Thunderbird Version: 78.11.0

Client Standalone:

OS: Windows 10
Sieve Version: 0.5.2

Mailcow:

OS: Ubuntu 20.04

Mailcow Versions:

acme-mailcow (mailcow/acme:1.78)

clamd-mailcow (mailcow/clamd:1.39)

dockerapi-mailcow (mailcow/dockerapi:1.38)

dovecot-mailcow (mailcow/dovecot:1.145)

ejabberd-mailcow (mailcow/ejabberd:1.5)

ipv6nat-mailcow (robbertkl/ipv6nat)

memcached-mailcow (memcached:alpine)

mysql-mailcow (mariadb:10.5)

netfilter-mailcow (mailcow/netfilter:1.41)

nginx-mailcow (nginx:mainline-alpine)

olefy-mailcow (mailcow/olefy:1.7)

php-fpm-mailcow (mailcow/phpfpm:1.74)

postfix-mailcow (mailcow/postfix:1.61)

redis-mailcow (redis:5-alpine)

rspamd-mailcow (mailcow/rspamd:1.76)

sogo-mailcow (mailcow/sogo:1.98)

solr-mailcow (mailcow/solr:1.7)

unbound-mailcow (mailcow/unbound:1.13)

watchdog-mailcow (mailcow/watchdog:1.91)

-- Sent from: http://dovecot.2317879.n4.nabble.com/