For most companies, email is the business’s working memory: contracts, customer correspondence, quotes and years of history. When the mail server changes, whether because of the old host’s limits or a move to a dedicated business mail server, there are two main concerns. No message, old or new, can be lost, and staff’s daily work must not stop. A phased approach achieves both.
Step 1: Take inventory
Before anything else, get a complete picture of the current setup:
- A list of all mailboxes and the size of each
- Aliases, forwarders and distribution groups
- Autoresponders, filters and server-side rules
- Calendars and address books, if they are on the current server
- Users still on POP3, whose email exists only on their own computers
- Every device and application that sends email through this server, such as the website, finance software, copiers and scanners
Step 2: Prepare the new server
- Create the domain and all mailboxes with the same addresses on the new server, and set quotas at least as large as current usage.
- Recreate aliases, groups and forwarders.
- Generate the new server’s DKIM key and publish its record, update the SPF record to include the new server’s IP, and ask the data center to set the PTR record for the new address.
- Install a valid SSL certificate for the server name, for example
mail.company.com, on the new server. - A day or two before the migration, lower the TTL of the MX records and the mail server name.
Step 3: Initial sync
Move old messages before migration day. The most common method is syncing mailboxes over IMAP with tools such as imapsync, or a migration tool provided by the destination server. These tools read messages folder by folder from the old server and write them to the new one. Each mailbox needs access on both sides: either the user’s password, or an admin account that some servers provide for this purpose. Large mailboxes can take hours, so start this step several days early.
After syncing, compare message counts for a few main folders on both servers. A simple check at this stage prevents surprises after the old server is shut down.
Step 4: Migration day
- Point the MX records and the mail server name to the new server.
- Don’t shut down the old server, because some senders will keep delivering to it for a while.
- A few hours later, and again a day or two later, run a follow-up sync so messages that reached the old server in the meantime are moved too. This run transfers only new messages.
- Update the SMTP settings of the website, applications and devices that send email.
Step 5: Users
If the server name in users’ settings stayed the same, Outlook and phones will connect to the new server on their own after the DNS change, though they may need to re-enter the password or re-add the account. Before the migration, tell users the timing, the new webmail address and what they will see. Migrate signatures, calendars and contacts separately, and upload POP3 users’ local email to the server after converting their accounts to IMAP.
After the migration
Keep the old server available for at least several weeks, and take a full archive backup before decommissioning it. Watch the outgoing queue, DMARC reports and bounced emails for a few days to make sure company email isn’t landing in spam. Once you’re confident, remove the old IP from the SPF record and restore the TTL to normal.
Checklist
- A list of mailboxes, aliases, groups and automated senders
- SPF, DKIM, PTR and SSL for the new server are ready before the migration
- Initial sync done and message counts compared
- MX changed and two follow-up syncs run
- Users informed and devices updated
- The old server stays active until you are fully confident
ITPlus724 engineers migrate business email to SmarterMail servers step by step, with full message sync, so your company’s staff never have to stop working.