You can send letters abroad up to a maximum weight of 2,000g. The maximum dimension is length + width + height = 900 mm, with a maximum length of 600 m.
Content, Format & Weight
Excluded from postal transportation are items of correspondence,
which do not comply with the conditions set forth in the Universal Postal Convention and the Supplementary Provisions,
that do not comply with the provisions specified in the GTC, and
sent in support of fraudulent acts or with the intention of evading full payment of the relevant charges.
Dangerous Goods
Tracking and tracing for international letter mail items always requires a shipment code (10-digit registered mail number). For this reason, the additional service Registered Mail International always offers the option of tracking and tracing.
Most foreign postal companies (country of destination) also provide us with their receipt log for information purposes when processing incoming mail. Many postal companies provide further information.
Tracking
Yes, because this is the only way to ensure that your items are transported "prioritaire", i.e. by the fastest route, even abroad. Alternatively, you can also affix the relevant "Priority/Prioritaire/Air Mail" notices clearly printed on the item.
Make Your Shipments Proper
More information on the Universal Postal Union can be found here.