This topic might help a bit: https://www.lansweeper.com/forum/yaf_postst13336_Shared-office-365-mailbox.aspx
However, for your helpdesk mailbox we strongly recommend using a secured, dedicated mailbox. We recommend enabling security as your helpdesk will likely contain sensitive information. We recommend a dedicated mailbox as Lansweeper will import all mails (old and now) from the designated inbox folder and treat them as helpdesk requests. All emails that don't meet your ignore rules will be imported into your helpdesk and moved to the helpdesk_archive folder, mails that meet the ignore filters will be moved to the helpdesk_ignore folder and not imported.