Use your own domain
Aliases normally live on isymail.com. Point a domain you own at us instead and the address you hand to a shop is yours, so it keeps working even if you stop using TMailr and it says nothing about who you use.
We re-check daily that the domain is still yours, because domains expire and change hands. If the record goes missing we write here once to warn you, and once more if we have to stop accepting the mail. Nothing else is ever sent to it. Leave it empty and we simply will not be able to tell you.
A subdomain is usually the right answer. Pointing a domain that already receives mail at us takes over all of it.
Use a subdomain unless you mean it
Mail routing is set per domain, so pointing yourcompany.com at us sends all of its mail here, including the mail you already get. Pick something like alias.yourcompany.com and nothing you currently receive is affected.
What we ask you to add
One TXT record so we can tell the domain is yours, and one MX record so mail for it reaches us. We check both and tell you exactly which one is missing. Proving the domain is yours changes nothing about where your mail goes; only the MX record does that.