Posti has stopped all mail deliveries by air at the turn of the year. This means, that the delivery time for letter mail will slow down in some areas in Finland. For example, express mail from Helsinki to Kemijärvi will arrive at the earliest on the second business day of posting.
This is good to take into account when ordering a visa. Lähialuematkat is not responsible for delays caused by the carrier.
You can check the timing from the Posti delivery time search: https://support.posti.fi/fi/tyokalut/toimitusaikakysely.html