PHP Version 7.3.21
@Nishit the PHP version seems to be good.
I tried to make changes to the code and I replaced the values with Null.
If you really don't know what you are editing I don't suggest to edit the core code also if I can understand your try to fix.
I think "we" need wait for a reply from developers.
What you can try is to resume the original core code that you edited than maybe you can test if you fet the same issue with a Gmail address or an email address that after the @ has domain.ext and not domain.ext.ext2
I remember to discovered (but I think is not reported as bug in GitHub) that UVdesk can have issue on receiving email on a subdomain address. I can remember I get error if my support email is like support1.team@domain.ext
In your case I'm not sure if the error can be realted to the domain extensions that have two fullstop .co.in.
Maybe not realted in this case you need wait a reply from devs.