Since new iRedMail server will install same components as old server, you
can choose what data you want to migrate. The major data are mail accounts,
roundcube webmail database, mailboxes.

Steps to migrate accounts, roundcube database, mailboxes:

- Setup a new server with the latest iRedMail, and make iRedAdmin-Pro-LDAP
work as expected.

- Export mail accounts from LDAP on OLD mail server.

Normally, LDAP data can be exported into LDIF format. Here's backup/export
script:
http://www.iredmail.org/wiki/index.php? … FAQ/Backup

After exported from old server, you will get a plain text file which has
LDIF data. You should remove top some items, includes:
+ dc=xxx,dc=xxx
+ cn=vmail,dc=xxx,dc=xxx
+ cn=vmailadmin,dc=xxx,dc=xxx
+ o=domains,dc=xxx,dc=xxx

Because we will use these ldap objects on new server, so remove them from
exported data.

Let's assume the exported backup data is saved in file /root/old.ldif

- Now, log into phpLDAPadmin with cn=Manager,dc=xxx,dc=xxx on NEW server,
remove object of your mail domain. it should be:

domainName=your_domain.com,o=domains,dc=xxx,dc=xxx

Remove all sub-objects under this object.

- Import /root/old.ldif with phpLDAPadmin.

You can find a button named "Import" in phpLDAPadmin left panel.

- There're some changes to LDAP schema, please read all upgrade tutorials
for iRedMail-0.5.1, and apply LDAP data related upgradings.

For example:
http://iredmail.org/wiki/index.php?titl … ing_values

You can find all upgrade tutorials here:
http://www.iredmail.org/doc.html#upgrade_tutorial

- Export/import roundcube webmail database, and upgrade database to work with
new version of Roundcube.

http://trac.roundcube.net/wiki/Howto_Upgrade

- Simply copy all mailboxes to new mail server.

WARNING: please make sure maildir path which stored/configured in LDAP
will match the real path on file system, so that mail clients can find
them.

Maybe i missed some other steps, but they're all i can remember. Please try
to upgrade on a non-product server first, if it works well, then try it on
product server.