RDNG artifact comment email notification failed

HI,

We have observed issue with artifact email notification in RDNG project areas since week.
We used to receive email when we add comment in artifact but now this functionality is not working.

Below is error message in rm.log:

2015-11-16 04:26:15,041 [       http-bio-31443-exec-723]  INFO ibm.rdm.fronting.server.rrs.publish.PublishService  - GET: https://jazz07-31443.rchland.ibm.com:31443/rm/publish/resources/*?size=100&linksonly=true&ownLinks=true&fields=ds:dataSource/ds:artifact/(traceability/links/Link/(title|linkType|relation)|about|format)&modifiedsince=2015-11-15T20:05:07.951-0600&pos=0&projectURI=_vhBxBdeeEeOanpkK85E7dw&scoped=false&delPrjCtxID=_vhBxBdeeEeOanpkK85E7dw
2015-11-16 04:26:15,071 [       http-bio-31443-exec-723]  WARN ibm.rdm.fronting.server.rrs.publish.PublishService  - CRRRS6506E  The Publishing Items feed was not found at project https://jazz07-31443.rchland.ibm.com:31443/rm/process/project-areas/_vhBxBdeeEeOanpkK85E7dw


2015-11-16 01:15:32,291 [         RM-Task-Executor-1149]  WARN m.fronting.server.services.comments.CommentsHelper  - Could not find user with userId ../../jts/users/mkandala%40in.ibm.com
2015-11-16 01:17:21,317 [         RM-Task-Executor-1157]  WARN m.fronting.server.services.comments.CommentsHelper  - Could not find user with userId ../../jts/users/suyadsul%40in.ibm.com
2015-11-16 01:17:33,319 [         RM-Task-Executor-1157]  WARN m.fronting.server.services.comments.CommentsHelper  - Could not find user with userId ../../jts/users/suyadsul%40in.ibm.com

We are facing same issue on our another RDNG instance aswell.

Could you please help us in resolution of this issue.

Thanks and regards,
Suyash