Remove old thumnail photo appearing in Outlook/OWA

Hi All,

Have an odd issue. We have an old thumbnail photo/Outlook photo appearing for a cloud only DL. 

I am trying to remove it but cannot find any trace of this photo in the environment. So far I have tried the following: 

• Checked all 365/ Exchange / On-prem AD attribute settings

• Checked DNS for BIMI records

• Forced Outlook cache reset to confirm not local issue / tested present in OWA

• Re-created the impacted Distribution List

Does anyone have any other ideas of what else I can check/try?

Thanks in advance!