To disable SPAM filtering for individual mailbox as an end user:

• Login to user’s webmail (https://outlook.office.com)
• Settings > Mail > Block or Allow
• Check option: “Don’t move email to my Junk Email folder“
• Save changes

To disable SPAM filtering for individual mailbox as an admin (via PowerShell):

• Connect PowerShell to Office 365
• Run: Set-MailboxJunkEmailConfiguration user.name -Enabled $false
  To verify status run: Get-MailboxJunkEmailConfiguration user.name

To disable SPAM filtering globally for all users withing organisation (via PowerShell):

• Connect PowerShell to Office 365
• Run: Get-Mailbox | Set-MailboxJunkEmailConfiguration –Enabled $False

May 2018
Office 365 / Exchange Online