Setting up cluster failover for IMAP

You can use a NOTES.INI setting to allow the IMAP server to support the ability for clients to fail over from one Domino® server to another when the user's primary mail server is unavailable.

About this task

This NOTES.INI setting controls the UIDVALIDITY value for folders to ensure they are different for each replica. Ensuring that the UIDVALIDITY value is different for replicas on different servers forces the IMAP-compliant clients to discard and re-fetch the cached data for messages in these folders, also ensuring that the IMAP client is synchronized with the replica being accessed after a failover.

Without the setting, the results when accessing multiple replicas would be unpredictable if the IMAP client cached information about messages in one replica that would not match the content in another replica. This could happen if the UIDVALIDITY value matched for a particular folder, but the content of the folder differed in any way.

Note: After enabling the setting, it is also necessary to disable and then enable IMAP for any database that uses it.

Procedure

On any clustered Domino® server in a cluster that is running the IMAP protocol, edit the NOTES.INI file.
For the following parameter, set n to a decimal number from 0-255.
```
IMAP_UIDVALIDITY_ROOT=n
```
Repeat for each IMAP server in the cluster, setting n to a different decimal number. For example, in a cluster of 5 servers, the value would be set to 1 on one server, 2 on the second server, 3 on the third and so on.
Use the convert task to disable and then re-enable IMAP support for any databases on the server that use it. For example, from the server console, issue the following command for a database called mymailfile.nsf:
```
load convert -e- mail\mymailfile.nsf
```
After IMAP support is disabled for all databases, use the convert task to re-enable IMAP support for each database. For example, from the server console, issue the following command for a database called mymailfile.nsf:
```
load convert -e mail\mymailfile.nsf
```

Results

The UIDVALIDITY values used for each folder will then be unique, as they will contain the "root" value specified via the NOTES.INI setting.

Once IMAP has been enabled, a database is immediately available for IMAP access within the cluster. It is not necessary to complete these steps on every replica of a mail file before allowing access to those that have been re-enabled after setting the NOTES.INI parameter.