Ask HN: Cheap shipping companies in Europe?

Anyone who owns an online store, selling physical goods, or someone who could help me on this matter?

What services do you use to ship the products(in Europe)? How do you handle the shipping products?

Until now i found that my country(Portugal) post-office service is cheapest way too ship across the Europe, but it is still very expensive, around 18 EUR per 2kg.

Thanks!