Redmine

Hi dear redmine-people

I have problems fetching imap mails. Does anyone have an idea what could be wrong here?

ENVIRONMENT
Ubuntu 16.04.4 LTS
redmine 3.4.4.stable
rake, version 12.3.0
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-linux]
rails 4.2.8
database mysql

CALL
When I call (commandline / cronjob)
rake -f Rakefile redmine:email:receive_imap RAILS_ENV=production host=xxx.domain.at port=1143 username=xxxx password='xxxxxx' ssl=true unknown_user=accept no_permission_check=1 --trace

ERROR
The Error I get
Invoke redmine:email:receive_imap (first_time)
Invoke environment (first_time)
Execute environment
(eval):53: warning: key :format is duplicated and overwritten on line 53
Execute redmine:email:receive_imap

MAIL
Mail I send to the user that fetches the mails:

subject: "Test-Mail-Ticket"

body: This is a new issue that will be added to project xxxx.
[description01]

Autor: User1
Status: New
Priorität: Normal
Zugewiesen an: User1
Kategorie:
Zielversion:

Thank you!
best regards
KC-IT-Team