S4B missed chat conversation subject line is having incorrect email address

Hi,

We are using S4B online. 

We recently observed the missed conversation in skype for business is showing incorrect email adress with unidentified format.

Missed conversation Subject line Sample : 

Missed conference with Karthik Sundara (SEIT), sippooldb41e12.infra.lync.com58395565-e0c1-4d2a-9c29-27602d588068@online.lync.com, Moorthy Urkavala (SEIT), 44da120c-2f10-4df5-9bff-5a9cace3f559@anonymous.invalid

Do we have any idea why its happening and we observed in recent days that is happening for group chat and occuring more users.