Surprisingly, after several months of using Alfresco 4.2.c the language of the “Recent Activities” notification email, which is automatically sent out by the Alfresco server, changed from spanish to english after no modifications on the server configuration at all.
To force using a specific locale on the Tomcat JVM, hence on Alfresco, just edit the following script:
and add the following localisation parameters to the JAVA_OPTS environment variable:
-Duser.country=ES -Duser.region=ES -Duser.language=es
Just replace ES for your desired language short code. That worked for me.