IMAP

The Axigen Solution: Overview & Architecture

The Axigen IMAP module establishes connection with IMAP clients and retrieves mail messages from the storage unit. The server accepts connections as specified by the IMAP listeners defined in the configuration file. By default the server accepts connections on 127.0.0.1:143 .

IMAP module overview

The IMAP module implements the extension QUOTA, as described by the RFC 2087 standard. IMAP clients implementing the QUOTA extension can display mailbox quota for a specific user account.

Listeners

Listeners can be defined and managed to add extra flexibility and configurability to this service. For that, global access limitations, SSL Settings and access lists can be enforced on the address used by this service for binding.

Access control

Access rules allow you to control connection to this service by defining simple access lists for specific Networks / IP Ranges / IP’s. Service level access rules are automatically applied to all its listeners and will override for this service any existing Global Access rules.

Flow control

Flow control parameters can be adjusted to fine tune the server’s performance and avoid overloading it. Global access limitations to this listener can be enforced by setting the total number of simultaneous connections, concurrent connections from each remote IP address, number of new connections to the listener made in a time period interval, number of total connections from each remote IP address on a time interval period. The default interval for this time period is set to 1 minute.

Logging

All Axigen main services can log different types of events. You can specify what events are logged, where and how they are logged.

Encryption and authentication

Various authentication types can be used in Axigen for IMAP secured (SSL/TLS) / unsecured connections. Possible options are: normal login, plain, login, cram-md5, digest-md5 and gssapi.

Error control

To protect the server, the number of failed/wrong commands received from IMAP clients during one session can be limited. When these limits are exceeded, incomplete connections or connections that are not RFC compliant will be dropped thus freeing important bandwidth.

If you do not specify a limit for the maximum number of (authentication) errors allowed for a IMAP client's session, security risks may arise.

Thread management

The Axigen mail server is designed to run on different machine configurations and operating systems, on networks with various traffic loads, structures, domain configurations, user rights etc. That is why, depending on all these variables, you can adapt the workload to the server’s processing power to improve its performance or avoid overload by setting the minimum and maximum number of threads that can be opened at a specific moment of time.

Compatibility with various IMAP mail clients

Axigen has been thoroughly tested and it is proven to work with Outlook, Thunderbird, Email Client OS X, Email Client Win 8.1

Public folders

Users may share email messages by simply copying and/or moving them to a public folder. You can also associate a certain email address with a public folder. Thus, emails can be sent directly to the public folder.

Internationalized search

When running an IMAP search for any IMAP client, the search text may contain language-specific characters (i.e. using diacritics).

IMAP ID support

Starting with version X2 Axigen implements the IMAP ID extension (RFC 2971).

A configuration option at the IMAP service level allows a system administrator to disable it but it should be noted that some features (e.g. auto-migration) depend on this feature being enabled.

IMAP LIST behavior

Note: starting with Axigen X2 the Axigen server no longer lists special folders (Calendar, Contacts, Notes, etc) in the answer to the IMAP list command.

There is a configuration option, called imapShowAllFolders that allows the system administrator to revert to the old behavior, avaiable at the IMAP service level.

 

Axigen X2 also makes use of a proprietary attribute that tells it to add special folders to the answer to a LIST command, called "X-AXI-ALL-FOLDERS".

That means that even if imapShowAllFolders is set to false, using

. list (X-AXI-ALL-FOLDERS) "" "*"

will tell Axigen to include the special folders as part of the IMAP LIST response.