need help to select some string in a pattern

[wqhhust]

I have the following pattern

#my.domain.host1#my1.domain.com#....
#my.domain.host2#my2.domain.com#....

And I want to select the string between the second and the third #. How to customize it?
If I am using the following, it will match all the string fro the beginning to the .com.
set -g @copycat_search_C-s '#.*.com'