Callback Campaign emails

Hopefully this is the right subforum, I'm not sure.

Anyway, my partner and I decided to come back to the game after being gone for about 6 months. A mutual friend was also planning to return, and said that one of their friends had sent them an email for the Callback Campaign and that we should wait so they could invite one of us. The only problem was that they hadn't received their email after a day or two (despite the site saying "Invitation e-mails will be sent once per day"). I didn't want us all to be waiting for that one email, so I just bought my sub (I don't really need the invitee items anyway) and invited my partner back. That was yesterday evening, and he still hasn't received his invite.

I know I sound impatient, but I'm mainly looking for info from people who have successfully sent and received these invites. Do they actually get sent out once a day, or once a week like I've seen some people on Reddit say?

We did it in the previous campaign (got my wife to come back so I had accurate knowledge of her email status) and it took more than a week. I invited her back on Sunday and the invites only went out on Monday (or something like that), but because I had unwittingly left it so late I missed the cut off for that Monday’s batch of emails and had to wait until the Monday after. Sort of annoying as we wanted to play right away.

It's such a bizarre system. It says they get sent out once a day, but it can sometimes take over a week? Why can't it be done automatically? Is it a sole person's responsibility to send out all of these emails one by one or something? I wanted the gold chocobo feathers for a mount I've wanted for a while, but honestly it's not really worth waiting a whole extra week to be able to play (since we agreed to only play the new content together).

UPDATE: My partner received his email while I was typing this. For anyone who ends up here looking for answers like I did, I sent one invite on Sunday night, then impatiently sent another on Monday night, and he received an invite very very early on Tuesday morning.