Yesterday I tried to clear 2 parcels containing Christmas gifts through customs. These originated outside of the EU. These were not high-value items so no customs duty to pay, but required clearance even so.
One of the parcels was announced via a letter in our postbox. I followed the link given in that letter, went through the process and everything worked well. I used the English language option and that was good. So no problem.
I was notified about the 2nd parcel via email. When I followed the link in the email I got a message that the system was down for maintenance (in the week before Christmas!) so I should try again in a few hours.
I tried again at various times yesterday but no change. I tried again at 07:30 today and got the same message with the note that the system would be down from 09:00 to 13:00. Strange.
Anyway, the point of this post is that I just followed the link I got in the snail-mail notification - https://tulli.fi/tullaa-pakettisi - but provided the reference number from the email notification. That worked OK. So if you are stuck trying to clear a parcel through customs using a link you received in an email, try this link instead.