Migrate one business mailbox from Rackspace to Google Workspace.

Description
Looking for an experienced Google Workspace / email migration specialist to migrate one business mailbox from Rackspace to Google Workspace.

Current setup

1 mailbox: TBA
Current provider: Rackspace
Domain registrar: 123 Reg
Website hosted on Squarespace (must remain unaffected)

Scope of work

Set up Google Workspace mailbox
Migrate all historical email from Rackspace via IMAP
Update DNS in 123 Reg, including:
MX records
SPF
DKIM
DMARC
Ensure no data loss
Minimise or avoid downtime during cutover
Test send/receive and deliverability (Gmail / Outlook / Yahoo)
Confirm Squarespace website and domain remain unaffected
Provide short handover / summary when complete

IMAP details

Server: secure.emailsrvr.com
Port: 993
SSL enabled