Service Desk Results in Rejected for Internal Users

Hello, I am configuring incoming mail and service desk on gitlab running on a linux host. It works perfectly for external users but gives a rejected mail for internal users
Our external users are able to send in mails and it gets registered on Service Desk.
I would appreciate some insight.

Please see below for my configuration:

gitlab_rails[‘service_desk_address’] = ‘helpdesk@domain.com’

gitlab_rails[‘smtp_enable’] = true
gitlab_rails[‘smtp_address’] = ‘mail.domain.com
gitlab_rails[‘smtp_port’] = 587
gitlab_rails[‘smtp_user_name’] = ‘helpdesk’
gitlab_rails[‘smtp_password’] = ‘password’
gitlab_rails[‘smtp_authentication’] = ‘login’
gitlab_rails[‘smtp_enable_starttls_auto’] = true

gitlab_rails[‘smtp_tls_cert_path’] = ‘/home/oo_oo/******-com-chain.pem’

gitlab_rails[‘incoming_email_enabled’] = true

gitlab_rails[‘incoming_email_address’] = “helpdesk-%{key}@domain.com
gitlab_rails[‘service_desk_email_address’] = “helpdesk-%{key}@domain.com

gitlab_rails[‘incoming_email_email’] = “helpdesk”
gitlab_rails[‘incoming_email_password’] = ‘password’

gitlab_rails[‘incoming_email_host’] = “mail.domain.com
gitlab_rails[‘incoming_email_port’] = 993
gitlab_rails[‘incoming_email_ssl’] = true

gitlab_rails[‘incoming_email_expunge_deleted’] = true
gitlab_rails[‘incoming_email_start_tls’] = false
gitlab_rails[‘incoming_email_mailbox_name’] = “Inbox”
gitlab_rails[‘incoming_email_idle_timeout’] = 60

gitlab_rails[‘service_desk_email_log_file’] = “/var/log/gitlab/mailroom/mail_room_json.log”

gitlab_rails[‘incoming_email_delivery_method’] = “sidekiq”
gitlab_rails[‘service_desk_email_delivery_method’] = “sidekiq”

gitlab_rails[‘gitlab_email_from’] = ‘helpdesk@domain.com’
gitlab_rails[‘gitlab_email_reply_to’] = ‘helpdesk-%{key}@domain.com