Why was the plusnet broadband firewall turned on this morning?

[#1]

Hello,
This morning at about 10:30 the plusnet firewall was turned on so I could no longer receive email via smtp. Some was still getting through via the he.net ipv6 tunnel so I was confused at first.
I had to change the firewall setttings on the plusnet website and reconnect to make things work again.
Very annoying. What if I'm on holiday and this happens?
I did reboot my debian router (which runs pppoe to connect to the fibre modem) after installing openssl updates, just to make sure every process has picked up the new library versions. Surely that shouldn't matter right?

[#2]

That'll explain why I've seen a drop in my mail traffic too then.
I've switched it off, although I'm not sure why I'll need to reconnect my PPP session, since it wasn't restarted when it was switched on?
I've had no notice that was going to happen.
Edit: I found the ticket where it happened, and it was on 2014-03-04 so it's been set to low for a month and I didn't notice ...
Edit the second: Which will coincide with my last PPP drop