How to Configure and Integrate iRedMail Services to Samba4 AD DC – Part 11

In this tutorial will learn how to modify iRedMail main daemons which provide mail services, respectively, Postfix used for mail transfer and Dovecot which delivers mail to accounts mailboxes, in order to integrate them both in Samba4 Active Directory Domain Controller.

By integrating iRedMail to a Samba4 AD DC you will benefit from the following features: user authentication, management, and status via Samba AD DC, create mail lists with the help of AD groups and Global LDAP Address Book in Roundcube.


  1. Install iRedMail on CentOS 7 for Samba4 AD Integration

Step 1: Prepare iRedMail System for Sama4 AD Integration

1. On the first step, you need to assign a static IP address for your machine in case you’re using a dynamic IP address provided by a DHCP server.

Run ifconfig command to list your machine network interfaces names and edit the proper network interface with your custom IP settings by issuing nmtui-edit command against the correct NIC.

Run nmtui-edit command with root privileges.

# ifconfig
# nmtui-edit eno16777736
Find Network Interface Name

Find Network Interface Name

2. Once the network interface is opened for editing, add the proper static IP settings, make sure you add the DNS servers IP addresses of your Samba4 AD DC and the name of your domain in order to query the realm from your machine. Use the below screenshot as a guide.

Configure Network Settings

Configure Network Settings

3. After you finish configuring the network interface, restart the network daemon to apply changes and issue a series of ping commands against the domain name and samba4 domain controllers FQDNs.

# systemctl restart network.service
# cat /etc/resolv.conf     # verify DNS resolver configuration if the correct DNS servers IPs are queried for domain resolution
# ping -c2 tecmint.lan     # Ping domain name
# ping -c2 adc1            # Ping first AD DC
# ping -c2 adc2            # Ping second AD DC
Verify Network DNS Configuration

Verify Network DNS Configuration

4. Next, sync time with samba domain controller by installing the ntpdate package and query Samba4 machine NTP server by issuing the below commands:

# yum install ntpdate
# ntpdate -qu tecmint.lan      # querry domain NTP servers
# ntpdate tecmint.lan          # Sync time with the domain
Sync Time with Samba NTP Server

Sync Time with Samba NTP Server

5. You might want the local time to be automatically synchronized with samba AD time server. In order to achieve this setting, add a scheduled job to run every hour by issuing crontab -e command and append the following line:

0   */1	  *   *   *   /usr/sbin/ntpdate tecmint.lan > /var/log/ntpdate.lan 2>&1
Auto Sync Time with Samba NTP

Auto Sync Time with Samba NTP

Step 2: Prepare Samba4 AD DC for iRedMail Integration

6. Now, move to a Windows machine with RSAT tools installed to manage Samba4 Active Directory as described in this tutorial here.

Open DNS Manager, go to your domain Forward Lookup Zones and add a new A record, an MX record and a PTR record to point to your iRedMail system IP address. Use the below screenshots as a guide.

Add A record (replace the name and the IP Address of iRedMail machine accordingly).

Create DNS A Record for iRedMail

Create DNS A Record for iRedMail

Add MX record (leave child domain blank and add a 10 priority for this mail server).

Create DNS MX Record for iRedMail

Create DNS MX Record for iRedMail

Add PTR record by expanding to Reverse Lookup Zones (replace IP address of iRedMail server accordingly). In case you haven’t configured a reverse zone for your domain controller so far, read the following tutorial:

  1. Manage Samba4 DNS Group Policy from Windows
Create DNS PTR Record for iRedMail

Create DNS PTR Record for iRedMail

7. After you’ve added the basic DNS records which make a mail server to function properly, move to the iRedMail machine, install bind-utils package and query the newly added mail records as suggested on the below excerpt.

Samba4 AD DC DNS server should respond with the DNS records added in the previous step.

# yum install bind-utils
# host tecmint.lan
# host mail.tecmint.lan
# host
Install Bind and Query Mail Records

Install Bind and Query Mail Records

From a Windows machine, open a Command Prompt window and issue nslookup command against the above mail server records.

8. As a final pre-requirement, create a new user account with minimal privileges in Samba4 AD DC with the name vmail, choose a strong password for this user and make sure the password for this user never expires.

The vmail user account will be used by iRedMail services to query Samba4 AD DC LDAP database and pull the email accounts.

To create the vmail account, use ADUC graphical tool from a Windows machine joined to the realm with RSAT tools installed as illustrated on the below screenshots or use samba-tool command line directly from a domain controller as explained on the following topic.

  1. Manage Samba4 Active Directory from Linux Command Line

In this guide, we’ll use the first method mentioned above.

Active Directory Users and Computers

Active Directory Users and Computers

Create New User for iRedMail

Create New User for iRedMail

Set Strong Password for User

Set Strong Password for User

9. From iRedMail system, test the vmail user ability to query Samba4 AD DC LDAP database by issuing the below command. The returned result should be a total number of objects entries for your domain as illustrated on the below screenshots.

# ldapsearch -x -h tecmint.lan -D '[email protected]' -W -b 'cn=users,dc=tecmint,dc=lan'

Note: Replace the domain name and the LDAP base dn in Samba4 AD (‘cn=users,dc=tecmint,dc=lan‘) accordingly.

Query Samba4 AD DC LDAP

Query Samba4 AD DC LDAP

Step 3: Integrate iRedMail Services to Samba4 AD DC

10. Now it’s time to tamper with iRedMail services (Postfix, Dovecot and Roundcube) in order to query Samba4 Domain Controller for mail accounts.

The first service to be modified will be the MTA agent, Postfix. Issue the following commands to disable a series of MTA settings, add your domain name to Postfix local domain and mailbox domains and use Dovecot agent to deliver received mails locally to user mailboxes.

# postconf -e virtual_alias_maps=' '
# postconf -e sender_bcc_maps=' '
# postconf -e recipient_bcc_maps= ' '
# postconf -e relay_domains=' '
# postconf -e relay_recipient_maps=' '
# postconf -e sender_dependent_relayhost_maps=' '
# postconf -e smtpd_sasl_local_domain='tecmint.lan'	#Replace with your own domain
# postconf -e virtual_mailbox_domains='tecmint.lan'	#Replace with your own domain	
# postconf -e transport_maps='hash:/etc/postfix/transport'
# postconf -e smtpd_sender_login_maps='proxy:ldap:/etc/postfix/'  # Check SMTP senders
# postconf -e virtual_mailbox_maps='proxy:ldap:/etc/postfix/'  # Check local mail accounts
# postconf -e virtual_alias_maps='proxy:ldap:/etc/postfix/'  # Check local mail lists
# cp /etc/postfix/transport /etc/postfix/transport.backup	# Backup transport conf file
# echo "tecmint.lan dovecot" > /etc/postfix/transport		# Add your domain with dovecot transport
# cat /etc/postfix/transport					# Verify transport file
# postmap hash:/etc/postfix/transport

11. Next, create Postfix /etc/postfix/ configuration file with your favorite text editor and add the below configuration.

server_host     = tecmint.lan
server_port     = 389
version         = 3
bind            = yes
start_tls       = no
bind_dn         = [email protected]
bind_pw         = ad_vmail_account_password
search_base     = dc=tecmint,dc=lan
scope           = sub
query_filter    = (&(userPrincipalName=%s)(objectClass=person)(!(userAccountControl:1.2.840.113556.1.4.803:=2)))
result_attribute= userPrincipalName
debuglevel      = 0

12. Create /etc/postfix/ with the following configuration.

server_host     = tecmint.lan
server_port     = 389
version         = 3
bind            = yes
start_tls       = no
bind_dn         = [email protected]
bind_pw         = ad_vmail_account_password
search_base     = dc=tecmint,dc=lan
scope           = sub
query_filter    = (&(objectclass=person)(userPrincipalName=%s))
result_attribute= userPrincipalName
result_format   = %d/%u/Maildir/
debuglevel      = 0

13. Create /etc/postfix/ with the below configuration.

server_host     = tecmint.lan
server_port     = 389
version         = 3
bind            = yes
start_tls       = no
bind_dn         = [email protected]
bind_pw         = ad_vmail_account_password
search_base     = dc=tecmint,dc=lan
scope           = sub
query_filter    = (&(objectClass=group)(mail=%s))
special_result_attribute = member
leaf_result_attribute = mail
result_attribute= userPrincipalName
debuglevel      = 0

On all three configuration files replace the values from server_host, bind_dn, bind_pw and search_base to reflect your own domain custom settings.

14. Next, open Postfix main configuration file and search and disable iRedAPD check_policy_service and smtpd_end_of_data_restrictions by adding a comment # in front of the following lines.

# nano /etc/postfix/

Comment the following lines:

#check_policy_service inet:
#smtpd_end_of_data_restrictions = check_policy_service inet:

15. Now, verify Postfix binding to Samba AD using an existing domain user and a domain group by issuing a series of queries as presented in the following examples.

The result should be similar as illustrated on the bellow screenshot.

# postmap -q [email protected] ldap:/etc/postfix/
# postmap -q [email protected] ldap:/etc/postfix/
# postmap -q [email protected] ldap:/etc/postfix/
Verify Postfix Binding to Samba AD

Verify Postfix Binding to Samba AD

Replace AD user and group accounts accordingly. Also, assure that the AD group you’re using has some AD users members assigned to it.

16. On the next step modify Dovecot configuration file in order to query Samba4 AD DC. Open file /etc/dovecot/dovecot-ldap.conf for editing and add the following lines.

hosts           = tecmint.lan:389
ldap_version    = 3
auth_bind       = yes
dn              = [email protected]
dnpass          = ad_vmail_password
base            = dc=tecmint,dc=lan
scope           = subtree
deref           = never
user_filter     = (&(userPrincipalName=%u)(objectClass=person)(!(userAccountControl:1.2.840.113556.1.4.803:=2)))
pass_filter     = (&(userPrincipalName=%u)(objectClass=person)(!(userAccountControl:1.2.840.113556.1.4.803:=2)))
pass_attrs      = userPassword=password
default_pass_scheme = CRYPT
user_attrs      = =home=/var/vmail/vmail1/%Ld/%Ln/Maildir/,=mail=maildir:/var/vmail/vmail1/%Ld/%Ln/Maildir/

The mailbox of a Samba4 AD account will be stored in /var/vmail/vmail1/your_domain.tld/your_domain_user/Maildir/ location on the Linux system.

17. Make sure pop3 and imap protocols are enabled in dovecot main configuration file. Verify if quota and acl mail plugins are also enabled by opening file /etc/dovecot/dovecot.conf and check if these values are present.

Enable Pop3 and Imap in Dovecot

Enable Pop3 and Imap in Dovecot

18. Optionally, if you want to set a global hard quota to not exceed the maximum of 500 MB of storage for each domain user, add the following line in /etc/dovecot/dovecot.conf file.

quota_rule = *:storage=500M 

19. Finally, in order to apply all changes made so far, restart and verify the status of Postfix and Dovecot daemons by issuing the below commands with root privileges.

# systemctl restart postfix dovecot
# systemctl status postfix dovecot

20. In order to test mail server configuration from the command line using IMAP protocol use telnet or netcat command as presented in the below example.

# nc localhost 143
a1 LOGIN [email protected]_domain.tld ad_user_password
a2 LIST “” “*”
Test iRedMail Configuration

Test iRedMail Configuration

If you can perform an IMAP login from the command line with a Samba4 user account then iRedMail server seems ready to send and receive mail for Active Directory accounts.

On the next tutorial will discuss how to integrate Roundcube webmail with Samba4 AD DC and enable Global LDAP Address Book, customize Roudcube, access Roundcube web interface from a browser and disable some unneeded iRedMail services.

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Matei Cezar

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11 Responses

  1. Razmo says:

    Hello, In the last versions of samba need to use TLS encrypted connections, otherwise, you cannot connect to LDAP.

    ldapsearch -H ldap://pdc1.domain.lan -D "cn=test1,cn=users,dc=domain,dc=lan" -W -s base -b "" supportedSASLMechanisms

    ldap_bind: Strong(er) authentication required (8)
    	additional info: BindSimple: Transport encryption required.

    I spent a lot of time-solving this problem.

    Here is my solution:

    To fix it, you need to copy /var/lib/samba/private/tls/ca.pem from samba ad server to centos 8 mail server folder /etc/pki/ca-trust/source/anchors/ and run update-ca-trust.

    Then comment string beginning at TLS_CACERT in file /etc/openldap/ldap.conf.

    Thereafter we can access to ldaps using simple authentication

    ldapsearch -H ldaps://pdc1.domain.lan:636 -x -D "cn=test1,cn=users,dc=domain,dc=lan" -W -s base -b "" supportedSASLMechanisms

    In postfix files,, and need modify lines

    server_host     = ldaps://pdc1.domain.lan:636
    #server_port     = 636 

    In dovecot file dovecot-ldap.conf need modify this lines.

    uris            = ldaps://pdc1.domain.lan:636
    auth_bind       = yes
    dn              = [email protected]

    Everything should work now.

  2. Trevor Lewis says:

    Hi, thanks in advance for the series of articles they proved very helpful in getting my setup completed, even managed to get iRedMail/SOGo integrated with AD users.

    My question is, how do I create alias domains e.g [email protected] maps to [email protected].


  3. Dmitriy Tkachenko says:

    Expression “ldapsearch -x -h tecmint.lan -D ‘[email protected]’ -W -b ‘cn=users,dc=tecmint,dc=lan'” won’t work. We get:

    "ldap_bind: Strong(er) authentication required (8)
           additional info: BindSimple: Transport encryption required."

    In last versions of samba there were some security updates applied restricting external applications to connect to AD using LDAP, unless they do not use or support TLS encrypted connections.

    To overcome this obstacle we should edit DC smb.conf in the following manner. Please add this string in [global] section:

    ldap server require strong auth = no

    And restart AD service:

    systemctl restart samba-ad-dc.service

    Not sure, whether we shall do such settings on the second DC server.

    • Matei Cezar says:

      ldap server requires strong auth = no parameter should be set to the second DC as well. When the LDAP client queries the domain it won’t know which dc server will receive and serve the query first.

  4. david says:

    I have this error when I type telnet mailhost 143

    In /var/log/dovecot.log, i have:

    imap([email protected]): Error Couldn't drop privileges: User i missing GID (see mail_gid setting)
    imap: Error: Internal error occurred, Refer to server information.

    Could you help me, please? Thank you

  5. david says:

    By typing the following command I’ve got the error.

    # postmap -q [email protected]  ldap:/etc/postfix/

    I have the following error :

    postmap: warning: dict_ldap_lookup: Search error -7: Bad search filter
    postmap: fatal: table ldap:/etc/postfix/ad_sender_login_maps_cf: query error:Success

    Could you help me please ? Thank you.

  6. david says:

    Thank you very much for this article, there is a typing error in systemd the service is networking.service and not network.service.

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