MailNickName or Alias attribute in Exchange Online doesn't match what is set in Exchange on-premises

Method 1: Use Exchange Management Shell

1. Change the existing Alias attribute value so that the change is found by Azure Active Directory (Azure AD) Connect. This should sync the change to Office 365. To do this, use either the Set-Mailbox or Set-RemoteMailbox cmdlet, based on the recipient type in Exchange on-premises. 
   
   Set-RemoteMailbox

   $alias=Get-remotemailbox user@domain.com
   Set-RemoteMailbox user@domain.com -alias "$($alias.alias)1"
   

   
   Set-Mailbox
    

   $alias=Get-mailbox user@domain.com
   Set-Mailbox user@domain.com -alias "$($alias.alias)1"
   

    
2. Start a Delta sync from Azure AD Connect, or wait for Azure AD Connect to run the delta. Ideally, this should sync the changes that are made in step 1 to Office 365.
3. Change the value of the Alias attribute to its original value. To do this, run either of the following cmdlets:
    

   Set-RemoteMailbox user@domain.com -alias "$($alias.alias)"

   Set-Mailbox user@domain -alias  "$($alias.alias)"
   

    
4. Start a Delta sync from Azure AD Connect, or wait for Azure AD Connect to run the delta> Ideally, this should sync the changes to Office 365.

Method 2: Use Active Directory PowerShell Module

1. Change the Mailnickname attribute value so that the change is discovered by Azure AD Connect. This should sync the change to Office 365. To do this, run the following set of cmdlets: 
    

   $mailnickname=Get-ADUser -Properties * -Filter {name -like 'username*'}
   Get-ADUser -Properties * -Filter {name -like 'username*'} | set-aduser -replace @{mailnickname="$($mailnickname.mailnickname)1"
   

    
2. Start a Delta sync from Azure AD Connect, or wait for Azure AD Connect to run the delta. Ideally, this should sync the changes that are made in step 1 to Office 365.
3. Change the value of the Mailnickname attribute to its original value. To do this, run the following cmdlet: 
    

   Get-ADUser -Properties * -Filter {name -like 'username*'} | set-aduser -replace @{mailnickname="$($mailnickname.mailnickname)"

    
4. Start a Delta sync from Azure AD Connect, or wait for Azure AD Connect to run the delta. Ideally, this should sync the changes that are made in step 1 to Office 365.