7.3.1

I often don't get registration emails. I guess it's around 20% of the time.

What process is used to send the emails? I'm sure this is not a UBB issue, but I want to tell my hosts what is used so they can track things more effectively.

at the bottom of it, the sendmail program is used on linux (usually)

it's called from the php mail() function, which is preconditioned by the phpmailer class (a standard that has been around for years -- and btw has a recent upgrade!!)

or.... if you use smtp, you need to make sure your smtp server is setup right and that your config is right.

at that bottom of that is the phpmailer class again, so i'd as your host about the 'sendmail' functionality and why there might be some sort of spam block or whatever

Cheers Sd