I'm migrating from ZImbra Collaboration Suite to Exchange 2010 SP1. I'm testing IMAPSync as a possible migration tool and have hit a problem with the IMAP server in Exchange 2010.

For each account it migrates, IMAPSync loops through the list of folders in the source mailbox and tests for the existence of each one in the destination mailbox. It then goes on to create those folders that do not exist and copy over the messages.

It's the intial testing for the existence of the folders that is giving me a problem. The response given by the Exchange server when the folder does not yet exist is given as an error:

"R=""16 NO IMAPSyncTest/8 doesn't exist.""

After ten of these errors have been issued in succession, the Exchange server appears to stop responding to the IMAP session. Enabling protocol logging for IMAP confirms that the 10th request for a non-existant folder is the last request to be logged on the server. IMAPSync carries on merrily without seeming to realise its connection has gone and thus fails to create any folders. I've logged this with the tool's creator.

Does anyone have any idea why Exchange is stopping responding to the connections though? The behaviour looks rather like throttling, although the 'ten strikes and you're out' trigger does not seem to correspond to any of the triggers on the ThrottlingPolicies. Just to check, I've tried creating a new ThrottlingPolicy, turned everything that I think might be relevant up to 11 and applied it to the my test mailbox. Policy settings are listed below, along with IMAP settings.

Everything else should be pretty much as default.

Throttling Policy

RunspaceId                                : afa3159c-32a6-4906-986f-8adfbe50868b
IsDefault                                 : False
AnonymousMaxConcurrency                   : 1
AnonymousPercentTimeInAD                  :
AnonymousPercentTimeInCAS                 :
AnonymousPercentTimeInMailboxRPC          :
EASMaxConcurrency                         : 10
EASPercentTimeInAD                        :
EASPercentTimeInCAS                       :
EASPercentTimeInMailboxRPC                :
EASMaxDevices                             : 10
EASMaxDeviceDeletesPerMonth               :
EWSMaxConcurrency                         : 10
EWSPercentTimeInAD                        : 50
EWSPercentTimeInCAS                       : 90
EWSPercentTimeInMailboxRPC                : 60
EWSMaxSubscriptions                       : 5000
EWSFastSearchTimeoutInSeconds             : 60
EWSFindCountLimit                         : 1000
IMAPMaxConcurrency                        : 1000
IMAPPercentTimeInAD                       : 400
IMAPPercentTimeInCAS                      : 400
IMAPPercentTimeInMailboxRPC               : 400
OWAMaxConcurrency                         : 5
OWAPercentTimeInAD                        : 30
OWAPercentTimeInCAS                       : 150
OWAPercentTimeInMailboxRPC                : 150
POPMaxConcurrency                         : 20
POPPercentTimeInAD                        :
POPPercentTimeInCAS                       :
POPPercentTimeInMailboxRPC                :
PowerShellMaxConcurrency                  : 18
PowerShellMaxTenantConcurrency            :
PowerShellMaxCmdlets                      :
PowerShellMaxCmdletsTimePeriod            :
ExchangeMaxCmdlets                        :
PowerShellMaxCmdletQueueDepth             :
PowerShellMaxDestructiveCmdlets           :
PowerShellMaxDestructiveCmdletsTimePeriod :
RCAMaxConcurrency                         : 1000
RCAPercentTimeInAD                        : 400
RCAPercentTimeInCAS                       : 400
RCAPercentTimeInMailboxRPC                : 400
CPAMaxConcurrency                         : 20
CPAPercentTimeInCAS                       : 205
CPAPercentTimeInMailboxRPC                : 200
MessageRateLimit                          :
RecipientRateLimit                        :
ForwardeeLimit                            :
CPUStartPercent                           : 75
AdminDisplayName                          :
ExchangeVersion                           : 0.10 (14.0.100.0)
Name                                      : TestMigrationThrottling
DistinguishedName                         : CN=TestMigrationThrottling,CN=Global Settings,CN=Our Company,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=cimex,DC=com
Identity                                  : TestMigrationThrottling
Guid                                      : 240049b3-2023-4df1-8edc-fbfc1fc80b87
ObjectCategory                            : domain.com/Configuration/Schema/ms-Exch-Throttling-Policy
ObjectClass                               : {top, msExchGenericPolicy, msExchThrottlingPolicy}
WhenChanged                               : 21/04/2011 18:48:19
WhenCreated                               : 21/04/2011 18:07:20
WhenChangedUTC                            : 21/04/2011 17:48:19
WhenCreatedUTC                            : 21/04/2011 17:07:20
OrganizationId                            :
OriginatingServer                         : a-domain-controller
IsValid                                   : True

IMAPSettings

RunspaceId                        : afa3159c-32a6-4906-986f-8adfbe50868b
ProtocolName                      : IMAP4
Name                              : 1
MaxCommandSize                    : 10240
ShowHiddenFoldersEnabled          : False
UnencryptedOrTLSBindings          : {192.168.x.x:143}
SSLBindings                       : {192.168.x.x:993}
InternalConnectionSettings        : {mail.office.domain.com:143:TLS, mail.office.domain.com:993:SSL}
ExternalConnectionSettings        : {mail.office.domain.com:143:TLS, mail.office.domain.com:993:SSL}
X509CertificateName               : mail.domain.com
Banner                            : The Microsoft Exchange IMAP4 service is ready.
LoginType                         : SecureLogin
AuthenticatedConnectionTimeout    : 00:30:00
PreAuthenticatedConnectionTimeout : 00:01:00
MaxConnections                    : 2147483647
MaxConnectionFromSingleIP         : 2147483647
MaxConnectionsPerUser             : 16
MessageRetrievalMimeFormat        : BestBodyFormat
ProxyTargetPort                   : 143
CalendarItemRetrievalOption       : iCalendar
OwaServerUrl                      :
EnableExactRFC822Size             : False
LiveIdBasicAuthReplacement        : False
SuppressReadReceipt               : False
ProtocolLogEnabled                : True
EnforceCertificateErrors          : False
LogFileLocation                   : C:\Program Files\Microsoft\Exchange Server\V14\Logging\Imap4
LogFileRollOverSettings           : Daily
LogPerFileSizeQuota               : 0 B (0 bytes)
ExtendedProtectionPolicy          : None
EnableGSSAPIAndNTLMAuth           : True
Server                            : CMX-OFFICE-EX01
AdminDisplayName                  :
ExchangeVersion                   : 0.10 (14.0.100.0)
DistinguishedName                 : CN=1,CN=IMAP4,CN=Protocols,CN=EXCHANGE01,CN=Servers,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=Our COmpany,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain,DC=com
Identity                          : EXCHANGE01\1
Guid                              : 48f9dc37-74c2-4fb0-a042-641f863f45f2
ObjectCategory                    : domain.com/Configuration/Schema/ms-Exch-Protocol-Cfg-IMAP-Server
ObjectClass                       : {top, protocolCfg, protocolCfgIMAP, protocolCfgIMAPServer}
WhenChanged                       : 21/04/2011 17:03:39
WhenCreated                       : 15/04/2011 13:51:58
WhenChangedUTC                    : 21/04/2011 16:03:39
WhenCreatedUTC                    : 15/04/2011 12:51:58
OrganizationId                    :
OriginatingServer                 : a-domain-server
IsValid                           : True