Originally Posted by kap
Can you confirm you are able to dns resolve chat.freenode.net? Start > Run:
cmd /k nslookup chat.freenode.net

Server:  cdns01.comcast.net
Address:  2001:558:feed::1

Non-authoritative answer:
Name:    chat.freenode.net
Addresses:  2a00:1a28:1100:11::42

You can also ping chat.freenode.net?

Pinging chat.freenode.net [2600:3c02::f03c:91ff:fe59:7d2e] with 32 bytes of data:
Reply from 2600:3c02::f03c:91ff:fe59:7d2e: time=82ms
Reply from 2600:3c02::f03c:91ff:fe59:7d2e: time=85ms
Reply from 2600:3c02::f03c:91ff:fe59:7d2e: time=88ms
Reply from 2600:3c02::f03c:91ff:fe59:7d2e: time=83ms

Ping statistics for 2600:3c02::f03c:91ff:fe59:7d2e:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 82ms, Maximum = 88ms, Average = 84ms

I'm not sure if your firewall can be queried with PowerShell, but are you sure there's no block on mirc.exe?

Get-NetFirewallProfile -Name Private | Get-NetFirewallRule | Where { $_.Action -eq 'Blocked' -and $_.Name -like '*mIRC*' }

No joy on that but I see TCP & UDP allowed inbound & no outbound rules in MSE.

Note: You may also run this with -Name Public