Where could I find Internet address of companies offering postal mail services, such as mailboxes in Helsinki? Thank You

If you wish to find out where there are post offices in Helsinki, or anything else about the postal services offered by the Finnish post company, please send an e-mail to the Finland Post Ltd, whose e-mail address can be clicked in their Internet page (in English): http://www.posti.fi/english/index.html

I am sorry if I have misunderstood your question, in which case please try to rephrase it and ask again.