title: How to assign custom attribute to Exchange Online Mailbox using Graph API?
body: <p>My task is to assign <a href="https://docs.microsoft.com/en-us/exchange/recipients/mailbox-custom-attributes?view=exchserver-2019&amp;viewFallbackFrom=exchonline-ww" rel="nofollow noreferrer">custom attribute</a> to mailbox in Exchange online using Graph API. Problem is that I cannot find endpoint corresponding to this attribute. It should be possible to set this attribute via Graph API because it could be done with powershell : <code>Set-Mailbox $UserName -CustomAttribute5 $sisSchool -AddressBookPolicy $sisSchool </code></p>
  <p>Maybe some of you have done something similar and could help me ? :)</p>
  <p><a href="https://i.stack.imgur.com/h3Mfq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/h3Mfq.png" alt="enter image description here" /></a></p>