Access shared/delegate mailbox of Exchange Server

1. Enable IMAP and POP3 protocols

Make sure you have enabled IMAP and POP3. Following articles can help you with that:

• How to enable POP3 in Exchange 2013
• How to enable IMAP in Exchange 2013

2. Turn on basic authentication

Exchange Management Console

• Open EMC, expand to Server Configuration->Client Access.
• In the middle panel, click your exchange CAS server, click POP3 and IMAP4 tab, right click IMAP4 and choose properties.
• In Authentication tab, select “Plain text logon (Basic authentication)”, then click OK.
• Open services.msc, restart Microsoft Exchange Transport services.

Power Shell

Set-IMAPSettings -Server -LoginType PlainTextLogin
Set-POPSettings -Server -LoginType PlainTextLogin

Open services.msc, restart Microsoft Exchange Transport services.

3. Add permissions to the shared mailbox

Give one user full access permission to the shared mailbox:

Add-MailboxPermission Shared.Mailbox1 -user John.Doe -AccessRights FullAccess

Note: You cannot add permissions for user without mailbox, Powershell is the only option in such case.

4. Access the shared mailbox

Exchange 2003

Use the following user format DomainName\Username\MailboxAlias
(e.g. DOMAIN\John.Doe\Shared.Mailbox1) to log into the shared mailbox.

Exchange 2007

Install this patch: http://support.microsoft.com/?kbid=949926

Use the following user format DomainName\Username\MailboxAlias
(e.g. DOMAIN\John.Doe\Shared.Mailbox1) to log into the shared mailbox.

Exchange 2010, Exchange 2013

Use the following user format DomainName\Username\MailboxAlias
(e.g. DOMAIN\John.Doe\Shared.Mailbox1) to log into the shared mailbox.

NAMESPACE command

You can also try using NAMESPACE command to obtain information about shared/public folders.

LoginPLAIN login as different user

You can try 3 parameter of LoginPLAIN to log in as a different user:

using (Imap imap = new Imap)
{
    imap.Connect(); // or ConnectSSL for SSL

    imap.LoginPLAIN("user@example.com", "admin@example.com", "admin_password");

    //...

    imap.Close();
}