Steps to Migrate Email from Gmail to M365 using MS Outlook

Video Guide on Migrate Emails Using Outlook Client on Windows

Legend:

Gmail account = Current @connect.hku.hk account on Google
M365 account = New @connect.hku.hk account on Microsoft

Turn on IMAP on Gmail

Logout from all Google accounts and open an Incognito/InPrivate browser.
Go to https://webmail.hku.hk and click the button CONNECT.HKU.HK (Google, read-only)
Login with your UID and password.
At the top right, click Settings and See all settings.
Click the Forwarding and POP/IMAP
In the “IMAP access” section, select Enable IMAP. Click Save Changes.
Under your account icon, click Manage your Google Account.
Under Security, in the Less secure app access section, set “Allow less secure apps:” to ON.
Please check all the labels in Gmail, to make sure all label doesn’t contain special character.
Rename any label with special character: ~ ` ! @ # $ % ^ & * ( ) _ + = { } | [ ] \ : ” ; ‘ < > , . ? /

Go to Control Panel, look up Mail (Microsoft Outlook).
Under Show Profiles, click Add. Under Profile Name, enter Migration and click OK.
Click Cancel under the Add Account page.
Click OK when you see the alert on create a profile with no email account.
Choose Prompt for a profile to be used, Click Apply and OK.

Open Outlook. Select the new Profile Name: Migration and click OK.
Enter your HKU Connect email address. Click Advanced options and click Let me set up my account manually.
Select Google.
Enter imap.gmail.com under Server of Incoming mail; enter 993 under Port; select SSL/TLS under Encryption method.
Enter smtp.gmail.com under Server of Outgoing mail; enter 587 under Port; select STARTLS under Encryption method.
Click Next.
Enter your HKU Portal PIN/Graduate Email Account Password. Click Connect.
Enter yourUID@connect.hku.hk and HKU Portal PIN/Graduate Email Account Password again.
The Google account permissions window may appear. Click Allow.
Once Outlook finishes adding your Gmail account, click OK.
Outlook may take hours to synchronize all mails to local computer. Please keep it online and wait until the Send/Receive status complete. You can click the Send/Receive bar at the bottom to check the progress and this bar will be gone after synchronization is completed.

Open Outlook. Select File, Open & Export and Import/Export.
Select Export to a file and click Next.
Select Outlook Data File (.pst) > Next.
Select the email account (@connect.hku.hk using Gmail) and Next.
Choose the preferred file destination, name the file and click OK. Then click Finish.
You can set a password to protect the exported .pst file, or you can leave it blank. Click OK.
After the export is completed, close Outlook.

After the export is completed, close Outlook.
Open Control Panel, look up Mail (Microsoft Outlook). Click Show Profiles and select the profile Migration. Click Properties, E-mail Accounts and New.
Type Your Name, Email address and Password and click Next. Click Finish.
Open Outlook and it shows both the Microsoft account (the upper one) and Google account (the lower one).

Right click the M365 account and select New Folder.
Add a name for the folder.
Select the newly created folder. Then select File, Open & Export and Import/Export.
Select Import from another program of file and click Next.
Select Outlook Data File (.pst)and click Next.
Choose the location of the imported .pst fileand click Next.
Select Import items into the current folder and click Finish. All emails from your Gmail account will be imported into the destination folder of your Microsoft account.
After importing the mails to your Microsoft account, if you find the imported folders are empty, click View, Change View and IMAP Messages for each imported folder and all emails will be shown.
Go to https://webmail.hku.hk and select the button CONNECT.HKU.HK (Microsoft 365). Double check if all the migrated emails can be read on webmail.
You can remove the temporary profile created if you don’t want to keep it. Close Outlook. Go to Control Panel and look for Mail (Microsoft Outlook). Click Show Profiles and select Migration. Click Remove and OK to confirm the deletion.

Please run the following script which could help to convert the imported mail folder(s) to Outlook native format.

Open the MS Outlook 365 Client
Download script file here (filename: fiximportedimapfolders.zip)
Extract the zip file. Open the extracted folder and double click the FixImportedIMAPFolders.vbs file
Click OK to run the file
Select the Outlook icon on task bar
You will see the follow windows. Select the Import from Gmail folder and click OK.
Select the following icon on Task bar
Click Yes, to include subfolders
Click OK to complete
The imported mails will show up on mobile Outlook/Mail app.

Credit: Solution was provided by howto-outlook.com .