If you need to add email aliases to O365 accts in bulk use the following (EMS) powershell command with the CSV file formatted this way:

 

Name	ProxyAddresses
user1@domainold.com	user1@domainnew.com

 

Run this in EMS:

Import-Csv C:\email-aliases.csv | ForEach-Object{ $name = $_.Name } 

Import-Csv C:\email-aliases.csv | ForEach-Object{ $proxy = $_.ProxyAddresses -split ‘;’} 

Set-RemoteMailbox -Identity $name -EmailAddresses @{add= $proxy} 

 

OR

 

Get the display name and email alias in this CSV format.

mailbox	newemailaddress
Phyliss Ames	pames@email.domain.com
Shelley Whitten	swhitten@email.domain.com

 

Run in EMS:

Import-CSV “C:\staging\aliases2.csv” | ForEach {Set-RemoteMailbox -identity $_.Mailbox -EmailAddresses @{add=$_.NewEmailAddress}}