3. Migration

3.1. What was migrated?

The following items were migrated from Herald/Webmail:

  • Email data from Herald IMAP mailstore

  • Contacts from Webmail

  • Preferred Sender from Webmail (if this was an Oxford address associated with the user)

  • Signature from Webmail

  • Quota (if >2GB, otherwise was set to 2GB)

  • Vacation Message/Setting

  • Forwarding Addresses

  • Whitelist/Blacklist

  • Move to Junk Mail SPAM setting (see below)

The following items didn’t get migrated:

  • Discard SPAM threshold

  • Webmail Contact Groups

  • IMAP flags

  • IMAP folder subscription list

3.2. How did the SPAM setting map across?

Nexus has SPAM filter settings of Low, Medium, High and Off, which mapped to a Herald equivalent of >7, >5, >3, and 0 respectively. The value from Herald was mapped across as per below:

0 -> Off

1 -> High(>3)

2 -> High(>3)

3 -> High(>3)

4 -> Medium(>5)

5 -> Medium(>5)

6 -> Medium(>5)

7 -> Low(>7)

8 -> Low(>7)

9 -> Low(>7)

10 -> Low(>7)

>10 -> Off

The ‘automatically delete SPAM over a certain threshold’ setting was not migrated to Nexus.

3.3. How did the items get migrated?

 Various techniques were used to push items from Herald to Nexus, all data was encrypted in transit via HTTPS or SSL secured IMAP.

  • Email - IMAP to Exchange Webs Services conversion

  • Contacts - Exchange Webs Services

  • Preferred Sender - HTTPS to powershell

  • Signature - Screenscape OWA Light

  • Quota - HTTPS to powershell

  • Vacation Message/Setting - Exchange Webs Services

  • Forwarding Addresses - HTTPS to powershell

  • Whitelist/Blacklist - Screenscape OWA Light

  • SPAM settings - HTTPS to powershell

  • Corrupt messages found during the migration process

 Some messages couldn’t be migrated as some element of their MIME structure was corrupt, or they couldn’t be stored in Exchange for some other reason. When a corrupt message was detected its subject was logged (and only the subject was logged). At the end of the migration process, the system walked the Herald mailbox and located all messages with subject lines that matched known corrupt messages. All those messages were bundled in one or more zip files. The majority of the messages in the zip file would have actually been in the Exchange datastore, but because only the subject of the corrupt message was logged we were unable to determine which message on Herald with that subject was the corrupt one, and thus we had to place all messages into the zip file.

 This ensured no data was lost during the migration process and left it down to the end-user's software to try to figure out the content. Some clients were more tolerant of these corrupt messages than others, but all would display an approximation of the "true" intended message.

 For some, the corrupt messages email/attachment were confusing and generated support requests, but this was the best we could do when moving the email between these different systems.

 We found a particular issue with files which had a mime type of application/applefile. A number of corrupt messages we saw had files of other types marked as applefile and this caused issues. If a user receivedan email with their corrupt messages in it or an email saying their migration was stopped due to the number of corrupt messages, we recommended searching for attachments with that mime type first as they were usually the cause of the problem.

 We also found that the zip files we produced would not open on some Mac machines, although they were fine on Windows, Linux/UNIX and other Macs. If the zip file appeared corrupt when opening on a Mac, we advised opening it on another machine, preferably a PC.

3.4. Error Codes in the Migration Picker

If an account failed to migrate it was marked the next morning (circa 9am) in the migration picker. For each failed account, a failure code was available. Codes were added/removed as issues were found and solved. The last used codes are listed below with an explanation for each.

Code Explanation Response
Non-Herald Routing This user didn’t route their main email address to Herald. None
ForwardAddress=PreferredAddress The forwarding address on Herald was the same as the address used by the Herald account to send email  - not supported on Nexus Change forwarding on Webmail prior to re-migration
ForwardAddress=HeraldAddress The forwarding address on Herald was set to username@herald.ox.ac.uk - this is not supported on Nexus Change forwarding on Webmail prior to re-migration
ForwardAddress=NexusAddress The forwarding address on Herald was set to username@nexus.ox.ac.uk - this is not supported on Nexus Change forwarding on Webmail prior to re-migration
Early Failure - Unknown An error occurred early in the migration process. This usually occurred when the migration system was under too much load. OUCS will investigate and schedule re-migration
Case Two folders with the same name but different case were found (for example, Sent and sent) Change folder names
Quotes One or more folders with double quotes in their name were found Change folder names
Slash One or more folders with trailing slashes in their name were found Change folder names
Clash One or more folders with reserved names that could not be remapped to foldername_Herald, as foldername_Herald already exists, were found Change folder names
Folder Select StartIndex A problem was found opening a folder on Herald - a folder rename is required Change folder names on OUCS advice
Mig-Failed Folder Read(1) A problem was found opening a folder on Herald/creating a folder on Nexus OUCS will investigate and schedule re-migration
Mig-Failed Folder Read(2) A problem was found opening a folder on Herald/creating a folder on Nexus OUCS will investigate and schedule re-migration
Mig-Failed Exch Folder Create A problem was found creating a folder on Nexus OUCS will investigate and schedule re-migration
Mig-Slash One or more folders with trailing slashes in their name were found Change folder names
EWS-Error A system error occurred during migration. A cached copy of the old user object prior to the mailbox being added stopped the migration tool accessing the true mailbox. This was more likely to occur at the start of the migration window. OUCS will investigate and schedule re-migration
Mig-Unknown A system error occurred during migration OUCS will investigate and schedule re-migration
Mig-Transporter A system error occurred during migration OUCS will investigate and schedule re-migration
Mig-Transporter PS A system error occurred during migration OUCS will investigate and schedule re-migration
Mig-Transporter(Died) A system error occurred during migration OUCS will investigate and schedule re-migration
Forward Corrupt A number of corrupt messages were found that could not be migrated. There were either too many messages or they were too large to bundle into a zip file and forward on Examine messages with subject lines as per personal failure email. Remove messages where possible and contact OUCS to re-schedule migration
Large Msg in Mailbox A number of corrupt messages were found that could not be migrated. One or more of these were too large to bundle into a zip file and forward on Examine messages with subject lines as per personal failure email. Remove messages where possible and contact OUCS to re-schedule migration
(no code) Ran out of time to migrate account or the account was disabled OUCS will re-schedule migration, most likely to a Sunday in the next couple of weeks. OUCS will contact all users informing them of the new migration date.

NB: The owner of the account being migrated should have got a message detailing what they needed to do or a generic "Unknown Error" message.

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