Registered in most postmaster tools, but at my rate of sending, this is only to have a chance of being herd if problems arise.
There were a few blockages over the years, the last ones came from Microsoft: once in a while they refuse to use A records if MX is not present, or just swallow your mails.
For the important mails to first-time recipients I ask to RSVP, which works out beautifully. People know that email can be unrealiable.