The only way you can use ts.domain.com without :7622 behind it, is by using the default teamspeak port which is 9987 for TS3 on UDP.
Well..... there is another way, but then you need to create a forward in your firewall or router. From 9987 external to 7622 internal. But if you do that you can just as well run your TS on port 9987.