What is the difference between "OtherMails" and "ProxyAddresses" when using PowerShell?

[fstorer]

Dear all,

From time to time we have to change the name of a staff member, and we usually keep the old email address (which is strictly related to the name) as an alias. I noticed that when I run the command "Get-AzureADUser" I get two properties called "OtherMails" and "ProxyAddresses". The old email appears in "OtherMails" but NOT in the "ProxyAddresses" (as an additional "smtp"). Is that normal? What is the difference between the two properties?

Thanks in advance for any clarification

Francesco  

[#2]

@fstorer 

Actually, when you rename the user, the UPN and Primary SMTP address of the user get updated.  In this case, the old primary email address is added as secondary email address. In Azure AD, the Primary SMTP Address and Alias Email Addresses are available in the ProxyAddresses attribute. Refer the below post to know more about how the proxyAddresses attribute is populated in Azure AD.

• How the proxyAddresses attribute is populated in Azure AD 

The OtherMails property is not related with the SMTP email address. This is a different property which populates the user's alternate email address which can be configured through Azure AD portal. Initially, I thought this is the email address that can be used for MFA or SSPR authentication, but this is not true since the email address for the Multi-factor authentication or  SSPR is stored in different place. 

Hope, the OtherMails property is currently returns only the Alternate email address which is configured under the user's contact information. Refer the below image.

Hope, @Vasil Michev  provide more insight.