In actual practice, I started receiving imported old mail within minutes. But importing goes on without you, you don't even have to be logged on to Gmail.
Be forewarned that you will be inundated with "new" mail at your One Address during the import process.
Gmail, for instance, is not just an email service but also has a mobile email client app by the same name.
The Gmail mobile app lets you read and reply to messages from not only your Gmail account, but also your Yahoo Mail address, Microsoft Office 365 account, and others.
Of course you want to import to your One Address all your email contacts from the other services, AND your old email saved on those services.
Another example is Boomerang, which adds new features and tools to Gmail and Outlook that help improve your writing and help you remember when to follow-up on messages.We use it to communicate with colleagues and friends, confirm appointments, save receipts, and restore forgotten passwords.At the same time, checking your inbox shouldn't be the focal point of your day, even though odds are you feel less stressed when you have fewer unread messages.Client apps almost always let you access multiple email accounts, giving you the option to see all your messages in one consolidate view.We also homed in on email apps for personal use, which nixed from consideration a few apps that tend to be more prominent in the business world, such as Microsoft Outlook (desktop app) and IBM Notes.You'll probably want to keep all your email accounts active and receiving mail, at least for a while.Those addresses are out there and if people don't know your new address, they have no other way to reach you. The name is a respected brand widely used by both personal and business users.I have three email accounts, and it's a nuisance to check each one.I also have trouble keeping my address books in sync, and when I'm looking for a certain message, I have to check in three places.This is a good opportunity to review and delete old mail you really don't need, and keep the keepers.Email is, in many ways, the digital hub of modern life.