Add list of domains to a send connector (Exchange 2010)

I've been tasked with setting up forced TLS connections with one of our customers. No problem says I, we do that with other customers. I just have to add their domains to the TLS only list. The customer sends me a list of 240 domains.

I've been trying with PowerShell but no luck so far.

$a = (Get-SendConnector "TLS Required").AddressSpaces
import-csv U:\TLS_Domains.csv | % { $a += $_.Domain }

This doesn't produce the desired results however. I think I'm on the right track, I just have to figure out how to properly format my CSV contents and import that into the AddressSpace.

I did an export of a Send Connector to see what I got and the resulting CSV looks like:

#TYPE Microsoft.Exchange.Data.AddressSpace
"Address","Type","Cost","IncludeSubDomains","Domain","IsSmtpType","IsX400Type","X400Address"
"*.domain.com","SMTP","1","True","domain.com","True","False",

Anyone have any tips?