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Mailbox Sharing


Cloudron 6 introduced IMAP mailbox sharing. This feature will work by default on new Cloudron 6 installations. For Cloudrons that were installed before 6.0, some manual steps are required to make mailbox sharing work.


Cloudron uses dovecot as the IMAP server. The default namespace separator in dovecot is .. However, this separator conflicts with the mailbox sharing feature This is because Cloudron Email server users the user's email as the username and email addresses have a . in the domain portion.

The solution is to migrate to using / as the namespace separator. New installations use this separator by default. Existing installations must be migrated manually to use this separator.

Automated migration

The reason this migration is not automated is because there is a small chance that email clients might have cached this separator. For such clients, one will have to re-add the email account. At the time of writing, we are collecting information on what possible mail clients will be affected. Roundcube, Rainloop, SOGo, Thunderbird do not have a problem, but you might have to logout and login again. On Android K-9, one has to 'Refresh Folder List' on the account.


Before proceeding, please check what separator is used by the mail server. You can do this by inspecting the file /home/yellowtent/boxdata/mail/dovecot/namespace_separator. If it has /, then you can skip this guide entirely. If it has ., then read on.


SSH into the server and run the following commands to migrate to / separator.

cd /home/yellowtent/boxdata/mail/vmail
find . -type f -name '*.sieve' -exec sed -e '/fileinto/{s,\.,/,g}' -i.bak '{}' \;
echo "/" > /home/yellowtent/boxdata/mail/dovecot/namespace_separator
docker restart mail

The above script creates a backup of all the sieve scripts. You can safely delete them once all your users have reported back that there are no issues.

find . -type f -name '*.sieve.bak' -exec rm '{}' \;