Hi Tengu.
A typed formal letter would most likely get a response from me, but I'm a bit old fashioned that way. Next a well written and formal and succinct email. Long rambling hand written mail take time to read. Worst of all are round robin unpersonalised type things, I tend not to read them. Also find out who you're writting too. Mail with no name on them tend not to be read unless I'm bored.
Hope this helps?
GB.