[Google-Desktop] Firewall settings changes to enable GDS indexing of GMail

I have seen numerous references here and elsewhere to firewalls being
the probable cause of difficulties in getting GDS (Google Desktop
Search) to index GMail. Nowhere have I seen it stated clearly whether
the Windows firewall or another firewall needs adjusting, or both.

My experience has been that the Windows firewall does NOT need
adjusting. However, I have found that there is a firewall built into my
modem/router and, once I braved its rather daunting manual and
user-interface, it was fairly easy to change its settings. After
signing into the router's web interface I needed to go into the
Security->Firewall Policy Configuration->Port Filters section and add
"filters" to allow inbound and outbound TCP access to ports 995 and
587.

Until I made this change Google Desktop had been unable to index GMail
messages, and I kept getting messages (over a period of many days) that
indexing of other files, web pages, etc was incomplete because GMail
indexing was in progress. Changing the firewall settings removed this
blockage.