Three years back I started sending welcome messages to new mappers on behalf of SOSM, using a simple tool chain based on the RSS feed of new mappers from Pascal Neis.
The message is not customised as from the beginning it was seen as a replacement for the welcome message that had gone away with the web site redesign. The text (in 4 languages, no Romansh version though) is designed to welcome the new contributor and give pointers to the resources available nationally.
Has it worked? Difficult to say, as the whole point was a replacement of something that existed before, we didn't expect drastic change and we didn't get it.
And, no, I'm not stopping :-)