CE Service Desk - what happened with my emails

Hello there!

I just install latest GitLab CE in virtual machine with Ubuntu Groovy Server.
I want to try to use Service Desk before I introduce it in my company.

I installed postfix and courier-imap and configured according to the documentation.

I can send and receive emails (via terminal)

pplaczek@u2010server2:~$ echo "This is not working again. Please help me." | mail -s "service-desk problem" gitlab+gitlab-instance-5fe145dd-monitoring-1-issue-@u2010server2
gitlab@u2010server2:~$ mail
"/home/gitlab/Maildir": 1 message 1 new
>N   1 pplaczek                        13/595   service-desk p
? 

I also can get this message via IMAP:

placzek@u2010server2:~$ telnet localhost 143
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS ENABLE UTF8=ACCEPT] Courier-IMAP ready. Copyright 1998-2018 Double Precision, Inc.  See COPYING for distribution information.
0 login gitlab gitlab
* OK [ALERT] Filesystem notification initialization error -- contact your mail administrator (check for configuration errors with the FAM/Gamin library)
0 OK LOGIN Ok.
0 select inbox
* FLAGS (\Draft \Answered \Flagged \Deleted \Seen \Recent)
* OK [PERMANENTFLAGS (\* \Draft \Answered \Flagged \Deleted \Seen)] Limited
* 2 EXISTS
* 2 RECENT
* OK [UIDVALIDITY 612873462] Ok
* OK [MYRIGHTS "acdilrsw"] ACL
0 OK [READ-WRITE] Ok
0 search unseen
* SEARCH 1 2
0 OK SEARCH done.

And I can see that the GitLab doing something with this message, but I don’t know exactly what, and why it doesn’t create a new issue…

{"severity":"INFO","time":"2021-02-10 08:21:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Idling"}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Processing started"}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"uid":18,"action":"asking arbiter to deliver","arbitrator":"MailRoom::Arbitration::Redis"}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Getting new messages","unread":{"count":1,"ids":[18]},"to_be_delivered":{"count":1,"ids":[18]}}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"uid":18,"action":"sending to deliverer","deliverer":"MailRoom::Delivery::Sidekiq","byte_size":594}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","delivery_method":"Sidekiq","action":"message pushed"}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Processing started"}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Getting new messages","unread":{"count":0,"ids":[]},"to_be_delivered":{"count":0,"ids":[]}}
{"severity":"INFO","time":"2021-02-10 08:22:07 +0000","context":{"email":"gitlab","name":"inbox"},"action":"Idling"}

What I’m doing wrong?

/etc/gitlab/gitlab.rb

#### Incoming Email Address
####! The email address including the `%{key}` placeholder that will be replaced
####! to reference the item being replied to.
####! **The placeholder can be omitted but if present, it must appear in the
####!   "user" part of the address (before the `@`).**
gitlab_rails['incoming_email_address'] = "gitlab+%{key}@u2010server2"

#### Email account username
####! **With third party providers, this is usually the full email address.**
####! **With self-hosted email servers, this is usually the user part of the
####!   email address.**
gitlab_rails['incoming_email_email'] = "gitlab"

#### Email account password
gitlab_rails['incoming_email_password'] = "gitlab"

#### IMAP Settings
gitlab_rails['incoming_email_host'] = "localhost"
gitlab_rails['incoming_email_port'] = 143
gitlab_rails['incoming_email_ssl'] = false
gitlab_rails['incoming_email_start_tls'] = false

#### Incoming Mailbox Settings (via `mail_room`)
####! The mailbox where incoming mail will end up. Usually "inbox".
gitlab_rails['incoming_email_mailbox_name'] = "inbox"
####! The IDLE command timeout.
gitlab_rails['incoming_email_idle_timeout'] = 60
####! The file name for internal `mail_room` JSON logfile
gitlab_rails['incoming_email_log_file'] = "/var/log/gitlab/mailroom/mail_room_json.log"
####! Permanently remove messages from the mailbox when they are deleted after delivery
gitlab_rails['incoming_email_expunge_deleted'] = true