Dovecot tries to resolve the user domain with DNS

[stephdl]

In a production system Dovecot sends out many DNS requests, trying to resolve the domain suffix corresponding to the LDAP user domain.

The request volume is high ~20000 per hour, it depends on the server workload.

Discussion
https://mattermost.nethesis.it/nethesis/pl/8k8jyq4s77y17bew4nkps178ee

[stephdl]

QA

• install 2 accounts provider, one LDAP and one SAMBA AD
• install mail : add-module ghcr.io/nethserver/mail:1.3.1-dev.2
• configure the mail server to use one account provider
• become mail1 : ssh mail1@::1
• verify the /etc/hosts of the dovecot container points to the IP of the domain controller

podman exec -ti dovecot cat /etc/hosts

....
....

#user_domain
127.0.0.1 ad.rocky9-pve4.org

• change the account provider of the mail module : settings > general page
• verify that the account provider has changed inside the /etc/hosts of the container

[nrauso]

tested: VERIFIED