# How to provide custom TURN server settings when using a classic email account **URL:** \ **Category:** Show and Tell\ **Tags:** classic-mailbox, server-config, chatmail\ **Created:** [April 12, 2026, 12:24pm UTC](https://support.delta.chat/t/how-to-provide-custom-turn-server-settings-when-using-a-classic-email-account/5045 "2026-04-12T12:24:14Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Janus](https://support.delta.chat/letter_avatar_proxy/v4/letter/j/c2a13f/32.png) [@Janus](https://support.delta.chat/u/Janus)\ **Post date:** [April 12, 2026, 12:24pm UTC](https://support.delta.chat/t/how-to-provide-custom-turn-server-settings-when-using-a-classic-email-account/5045/1 "2026-04-12T12:24:14Z")
I am using Delta Chat with an existing email setup, and I wanted to test calls in the android app. Unfortunately there is no UI to configure TURN server settings, and the builtin server is not reachable from my lan. So here are the instructions to configure the IMAP server to provide TURN server address to the client. **Prerequisites** 1. Existing coturn installation configured with `static-auth-secret`. 2. Existing dovecot installation used as a classic email account. The server is configured with virtual users database and runs as `vmail` system user. All user mailboxes are stored in `/home/vmail`. **What Delta Chat expects** The client fetches TURN server address and credentials from the IMAP server by reading INBOX metadata item `/shared/vendor/deltachat/turn`. The value should be a string of the form: ```auto server.address.or.domain:port_number:username:password ``` **TURN server credentials** When coturn is configured with `static-auth-secret` it expects temporary time-limited usernames and passwords for authentication. To generate the credentials place this script in `/etc/periodic/hourly/update-turn-server-credentials.sh`, or arrange to run it hourly using some other mechanism. ```auto #!/bin/sh turn_sever_address=turn.example.com turn_server_port=3478 static_auth_secret="your static-auth-secret value" now=$(date +%s) expires=$((now+3600*2)) password=$(printf "%s" "$expires" | openssl dgst -sha1 -hmac "$static_auth_secret" -binary | openssl enc -base64 -A) printf "%s:%s:%s:%s" "$turn_server_address" "$turn_server_port" "$expires" "$password" > /var/lib/turn-server-info ``` This will write the TURN server information and credentials valid for two hours in the format Delta Chat expects to `/var/lib/turn-server-info` every hour. Run this one manually once, and verify that `/var/lib/turn-server-info` exists and has the right format. **Dovecot configuration** We need to enable IMAP metadata support in the server, so Delta Chat can read TURN server info. To do that, in your dovecot config file add the section to configure attribute storage in plain files: ```auto mail_attribute { dict fs { fs posix { prefix = %{home}/attributes/ } } } ``` This sets the attributes storage directory in the virtual user’s home, next to the usual Maildir. Then inside the `protocol imap` block add `imap_metadata = yes`: ```auto protocol imap { imap_metadata = yes } ``` Restart the dovecot server after updating config file. **User-specific configuration** This needs to be done once for each new user. Write the TURN attribute using doveadm, the actual value is not important: ```auto doveadm mailbox metadata set -u "username" -s "" /shared/vendor/deltachat/turn x ``` Dovecot creates the actual directories and files in the user’s home. Now find the mailbox GUID for your user by running: ```auto doveadm mailbox status -u "username" guid "INBOX" ``` This will print something like: ```auto INBOX guid=888390389af833cdde ``` The string after = is the mailbox GUID that is used as a directory name. After that replace attribute file with a symbolic link to `/var/lib/turn-server-info`: ```auto ln -sf /var/lib/turn-server-info /home/vmail/username/attributes/INBOX_guid_here/vendor/vendor.dovecot/pvt/server/vendor/deltachat/turn ``` And verify the results by running: ```auto doveadm mailbox metadata get -u "username" -s "" /shared/vendor/deltachat/turn ``` This command should print the contents of `/var/lib/turn-server-info`. **Results** In my setup this allows sharing an existing coturn installation with other services, like galene. ---
**Author:** ![WofWca](https://support.delta.chat/user_avatar/support.delta.chat/wofwca/32/1702_2.png) [@WofWca](https://support.delta.chat/u/WofWca)\ **Post date:** [April 12, 2026, 6:56pm UTC](https://support.delta.chat/t/how-to-provide-custom-turn-server-settings-when-using-a-classic-email-account/5045/2 "2026-04-12T18:56:15Z")
Great work! If one doesn’t really care about persistent TURN credentials leaking, this can be further simplified, as I suggested here: > [@Can I add calls to my mail by adding a turn on HestiaCP?](https://support.delta.chat/t/can-i-add-calls-to-my-mail-by-adding-a-turn-on-hestiacp/4306/2): > > Just make the username a timestamp that is super far in the future. ---
**Author:** ![r10s](https://support.delta.chat/user_avatar/support.delta.chat/r10s/32/1513_2.png) [@r10s](https://support.delta.chat/u/r10s)\ **Post date:** [April 13, 2026, 8:04pm UTC](https://support.delta.chat/t/how-to-provide-custom-turn-server-settings-when-using-a-classic-email-account/5045/3 "2026-04-13T20:04:35Z")
first of all, welcome aboard, @Janus. then, thanks a lot for the guide! indeed, i heard questions about that here and there. good thing with this approach is that one does not need to annoy end user to tweak some more weird settings. nor devs then discussing if settings on that level of detail, for potentially few user, are worth the effort 🙂 thanks again ❤ ---
**Author:** ![bestman](https://support.delta.chat/letter_avatar_proxy/v4/letter/b/96bed5/32.png) [@bestman](https://support.delta.chat/u/bestman)\ **Post date:** [April 13, 2026, 8:47pm UTC](https://support.delta.chat/t/how-to-provide-custom-turn-server-settings-when-using-a-classic-email-account/5045/4 "2026-04-13T20:47:16Z")
It would be nice if it was simply packaged in an app so that any user could enter the turn key and gain access to calls.