Mail Merge is a feature of LibreOffice that allows you to write a template letter with predefined fields and then populate that template with fields from a database. This is very useful if you need to send the same letter to a number of people with only small changes like the name and address of the person you're sending it to.
How to use it
After downloading the mailmerge.odt file (below is the link) and opening it, you can use the macros contained in the document. Edit the template as you see fit and then run the macros using the menus:
Tools → Macros → Run Macros mailmerge.odt → Standard → Mail → DoManualMailMerge
NOTE: The macros connect to a database and will do nothing if that database is not available. So you can not expect it to just work from downloading the file alone.
How it works
The macro connects to a SQL database and populates the fields of the template. The output is stored in one big single PDF file to make printing easier.
The template and the DB configuration are specific to Lanedo but can be easily customized. Mail merge service