Routes

Mail to Europe primarily went over land via the Trans-Siberian Railway until it was closed due to the Russian Revolution. After that, mail went via sea, either via Suez or more commonly, via the USA or Canada. This lasted until 1924 when the Trans-Siberian Railway reopened.

There were special mailboxes set up in the Ports for the mailing of items via the British Post Office. Often, mail would be placed in one of the Chinese mailboxes by mistake which would then be forwarded to the British Post Office. This card from Swatow dated 21 April 1920 appears to have bypassed the British system and been marked as Postage Due, which was assessed as 10 centimes upon arrival in France.

The Soviet postal authorities did not open the Trans-Siberian Railway until September 2, 1923 after the Bolshevik revolution. Previously, the TSR was believed to have closed to international mail before the end of 1917 but details in the Canadian Philatelist appear to prove that it was in use until March 19, 1918 but this had definitely had ceased by April 29 19181. This, however, is contradicted by examples in HKSC Jn 369 showing mail from December 22, 1917 (although this article was marked "via America"). This example, dated 21 Sep 1917 from Swatow was routed via the TSR

Port Destination Routing
Wei Hai Wei GB Wei Hai Wei to Shanghai then by P&O to Singapore, Penang, Colombo, Aden, Port Said, then through the Mediterranean to Southampton then train to London
Wei Hai Wei Malta "Steamer to Dalny (91 miles) then S.M.R. (South Manchurian Railway) to Changchun where, because of change of guage, mail was transferred to a different train for onward transmission to Harbin by the C.E.R. (Chinese Eastern Railway). From Harbin, a junction for Vladivostok, the Trans Siberian Railway main line express trains took the mails to Moscow. From there the mail was sent on to Warsaw, and then to Berlin, Leipzig, Innsbruck, Rome, Naples and Syracuse (Sicily). From Syracuse, the Malta ferry S.S. Ljubljana (contracted in 1922 to carry mail three times a week between Syracuse and Malta) carried the mail to Malta, this cover arriving at Sliema on 7 October 1927"
HKSC Jn 364/30 Mr. Peter Pugh

Routes from the Treaty Ports are a large subject area that I have very little experience with so any information on this subject matter is greatly appreciated.

1 - Vol 65 #4 Jul/Aug 2014