POP / IMAP Migration

Migrating emails from the existing email service to Zoho Mail

Email migration from current email servers to Zoho Mail servers:

Zoho Mail offers a very simple solution to migrate emails from your existing email servers to the respective user account in Zoho Mail directly. The most recommended way to migrate emails to Zoho Mail is IMAP Migration. The impact of the change in email service is very minimal for the users. They can continue from where they left, as the email statuses and email folders are maintained and migrated in IMAP Migration. 

In case the previous email server does not support IMAP, then the emails can also be migrated via POP migration. 

Migration from GSuite:

In GSuite (Google Apps)/ Gmail accounts, the emails are organized under labels and the labels act like folders when accessed via IMAP. Gmail allows an email to be under more than one label, as per its behavior. During migration to Zoho Mail, the same email is migrated into different folders based on the labels applied to that email in the Gmail account. i.e. An email which has 4 labels, will be migrated 4 times and will occupy 4 times its size because of the duplication. 

Hence to avoid duplication and to handle this better, Zoho Mail provides additional specific options for migrations from GSuite (Google Apps)/ Gmail accounts. Refer here for detailed instructions.

Migration from Exchange/ Outlook:

If the previous email service was run by an in-house/ on-premise Exchange Server (without POP/IMAP support) or the users emails were in Outlook and available as offline PST files, then the administrator can use Exchange Migration Wizard to migrate the emails from Exchange Server/ Outlook to the respective user accounts in Zoho Mail. The Zoho Mail Migration Wizard also supports Hosted Exchange Environments, to migrate the emails using Outlook Profile details, connecting to the Hosted Exchange server. 

Advantages of IMAP Migration over POP:

If your emails are in a cloud-hosted email service like Google Apps or Yahoo or any other cloud email server which support IMAP Access, you can perform a server to server migration via IMAP from the Control Panel. 

Zoho Mail supports both IMAP and POP Migration, but IMAP Migration has more advantages compared to the POP Migration.

IMAP Migration

POP Migration

Migration of email along with folder details.

POP does not migrate along with folders. All emails are migrated to Inbox.

Email (Read/ Unread) Status is maintained. 

All emails are retrieved as 'Unread' when migration via POP.

Multiple Client support:

  • Emails are migrated even if accessed by other clients.
  • The emails are synced in multiple clients with state maintenance
  • The emails available in the source mailbox is synced along with folder and state information.
  • The emails sent by other clients are synced via IMAP.

Only Single Client support:

  • If there are multiple client requests, the email is provided only to a single client.
  • The emails retrieved via POP already are not available for migration.
  • The emails sent by other clients will not be migrated, as it is not supported by POP Servers
The migration via IMAP is generally faster than normal.
The migration report has detailed statistics. 
The migration via POP is slower than IMAP Migration.
Specific failures in migration can be tracked accurately.
The errors can be corrected and the migration can be rerun. 
The failures in migration in POP cannot be tracked accurately from the retrieving server (Zoho Mail in this case). 
Hence the failure information will be vague

Configuration details needed before Migration:

For both POP/ IMAP Migration, the following details are required. 

  • Name of the Server - Hostname of the IMAP Server or the POP Server from which the migration needs to initiated
  • Server Port - For source Server standard ports for SSL and Non-SSL are supported. 
    • Supported ports for IMAP  - 143 (Non-SSL), 993 (SSL) 
    • Supported ports for POP - 110 (Non-SSL), 995 (SSL) 
  • SSL Type - Only Trusted Certificates are supported. Self Signed SSL certificates are not supported due to security reasons
  • Migration Protocol - Choose if your migration protocol is POP or IMAP.
  • Source User Names and Passwords for the user accounts - Make sure that the source accounts have IMAP access turned On. 
  • Exclude Folder List - The administrator can exclude some folders like "Spam" to quicken the migration process. Further, they can ask the users to create a common folder and move the emails that need not be migrated. This folder can be provided in the commonly exclude list, which will apply for all users. 
  • Maximum Connection Limit - The maximum connection limit is the number of maximum connections accepted by the server at a given time. For example, if you provide 5 as the maximum connection limit when the migration is started, the migration process will be started simultaneously for 5 users. The migration process will be faster when there are parallel migrations happening between the servers. 
  • Path Prefix - Some IMAP servers expect the PATH Prefix details for connecting and retrieving emails via IMAP. 
  • Black Out Time - In case there is any known downtime for the server or particular times of the week during which the server is overloaded, specify the Day of the week, Time in 24-hour format (From 'x' hours to 'y' hours) and the corresponding Timezone. The migration would be paused during the specified time duration to avoid any migration failures due to that. The Blackout Time and Timezone are applicable, only if there are any predetermined Time Intervals, during which the migration should be paused. 

Source Server details for migration:

To add a new migration, you need to add the source server from which the emails should be migrated. You can also perform the migration in batches, and also from different servers if you have multiple domains hosted with different providers and want to migrate everything to Zoho Mail. 

  1. Login to https://www.zoho.com/mail
  2. Launch Control Panel, go to Mail Administration, and choose Migration.
  3. Select Add Migration, to provide server details for migration.
  4. Provide a title for the migration.
  5. Select the Migration Protocol as IMAP or POP based on your preference.
  6. Provide the Host-Name of the server, the Security type and the port number for migration. 
  7. Select if your migration is going to be done from Gmail or other services. Migration from Gmail follows a slightly different process, as described here.
  8. Provide the maximum connection limit for your server.
  9. In the Exclude Folder List option, add the list of folders that you want to skip during migration. Enter the names of the folders within double quotes ("Folder1"), in which case only that folder will be excluded. If you want all subfolders under a parent folder to be migrated enter the folder name followed by /* within double quotes ("Folder1/*"). For detailed information on the convention, refer here.
  10. Select Add Migration to save the server details. 
  11. You need to add the account details to be migrated as the next step. 

Source User details for migration:

After you have added the Server details, you will have to add the Account Details. 

You can add the accounts manually or import the details from a CSV file. However, make sure that you have the source and the destination account details ready. For each user added, the source credentials are checked with the server and the user gets added only if the source authentication is successful. 

Steps to add user accounts for Migration:

  1. Select Add Accounts to add the account details manually. 
  2. Provide the Source username/ Password and the Destination to which the emails should be migrated. 
  3. In the Folder Option, you can choose either the All Folders or Specific Folders option. 
  4. If you choose the All Folders option, in case of IMAP migration, you can choose to skip any folders during migration using the Exclude Folder List option. The skip folders will be handy when the admin rerun migrations for the same set of users for some new emails or missed emails. Enter the names of the folders within double quotes ("Folder1"), in which case only that folder will be excluded. If you want all subfolders under a parent folder to be migrated enter the folder name followed by /* within double quotes ("Folder1/*"). For detailed information on the convention, refer here.
  5. If you choose the Folder Specific option, in case of IMAP migration, you can specify the folders that need to be included in the Include Folder List. Enter the names of the folders within double quotes ("Folder1"), in which case only that folder will be included. If you want all subfolders under a parent folder to be migrated enter the folder name followed by /* within double quotes ("Folder1/*"). For detailed information on the convention, refer here.
  6. Choose if you want to migrate All Mails or those that fall within a specific date range from the Date Range option.
  7. This will be authenticated with the source server provided, once you click Add.

Convention for mentioning folders:

  • In case you want to mention a specific parent folder (E.g. Reports), enter it as "Reports".
  • In case there are multiple subfolders under Reports and you want to mention all the subfolders, enter it as "Reports/*"
  • In case there exists a subfolder under Reports named 2016, and you want to mention this particular subfolder, enter it like this - "Reports/2016". 
  • If you want to mention all the subfolders under Inbox, only the Marketing folder without the subfolders, and a specific subfolder, 2012, alone under the Sales Reports folder to be mentioned, you will have to type the Folder List like this - "Inbox/*", "Marketing", "Sales Reports/2012".

Steps to Import users from CSV file:

  1. Prepare an excel file or a Zoho Sheet with the headers Source, Password, Destination. You can optionally include a column Priority, which specifies the order in which users accounts need to be migrated.
  2. Fill in the details under the respective columns for the user accounts to be migrated.
  3. Save the file as a CSV file.
  4. Click Upload Accounts link in the Migration Accounts page.
  5. Choose the respective file and Click Ok to upload the accounts.
  6. The accounts added will be listed in the section.
  7. You will be able to modify the Server details or the Migration type before you start the migration. 
  8. Check whether all the accounts to be migrated has been listed in Accounts section. 

Authentication Errors

  • Make sure that the user has not changed the password of the source account when you run the migration. 
  • The access to the old server is still in place for the account, until the migration is completed. 
  • In case you are migrating from GSuite/ Google Apps servers, you may have to log in via the web once to authenticate the IMAP activity in your account. In this case, request the user to login to the Google Apps account from web and follow the steps listed in this help page for the error 'Web login required': https://support.google.com/mail/answer/78754
  • Similarly, even in Outlook.com, your source account access may be blocked on detection of activity from new IP Addresses. We request you to log in and allow access to the Zoho Mail IP addresses, listed there under Recent Activity. Select 'This was me' to trust the Zoho Mail IP addresses and proceed with the migration.

Start Migration Process

In the Control Panel, navigate to Migration under Mail Administration. Ensure that the source passwords are not changed after adding the users for migration. The password should be the same until the entire migration process is completed.You can add multiple migrations from different servers or from the same server for different sets of users to have a phased and planned migration. 

  1. The list of migrations you have added will be listed in the Migrations page.
  2. Click Start link, across the migration you have just added to start the migration. 
  3. The Migration will be scheduled and the status will be 'In Progress' for the migration that is currently running. 
  4. You can view the overall migration status in the listing, and detailed migration status in the Accounts section. 
  5. For IMAP Migration, detailed statistics along with folder information will be available. 
  6. Click the count under the Total field to view the detailed information about the folder-wise migration details.
  7. Under each account, the errors, if any, will also be listed with details. Click Failed to view the number of emails not migrated and the reason.
  8. The common reasons include: 
    • Email Size Exceeded  - If the size of the email in the source server exceeds the maximum size defined in the user's email policy, such emails will not be migrated. 
    • Mail already present - If the email is a duplicate of an email already in the user's account in Zoho, the duplicate emails will not be migrated.
    • Too many addresses - If the number of To Addresses in an email exceeds the permitted limit in Zoho Mail, the email will not be migrated.
    • Invalid Message  - If the email format is not as per the RFC definitions, with an incorrect header or email format, such emails will not be migrated.
    • Unable to Process - In case there are any internal processing errors during the migration of a particular email, such emails will be skipped during migration.
  9. Apart from the migration statistics, the administrator and the users will receive a summary of migration information after the completion.

In case of some failures like Internal Error, the administrator can migrate only selective folders instead of entire migration. This will optimize the runtime for the migration, by removing the duplicates and the check for duplicate emails. 


Suspension of Migration

During the process of migration, if the size of the emails migrated in the account, exceeds the allowed storage, the incoming emails may get blocked. Hence to avoid this, if the account reaches 80% of the allowed storage, the migration gets suspended(paused) temporarily. You can create more space either by deleting some of the old or unwanted emails in your previous account or by purchasing additional storage for your Zoho account.

Once you are confident that the account has enough space, you can resume the migration.

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