A full sync with 40k mails results in a 1.6 gb file, although only ~110mb are occupied.
This is not overly problematic as this space will be reused as the actual required size grows, but it's not pretty either.
It is not clear so far why we end up with such a large file. The size seems to imply that at some point we actually use 1.6 gb, but end up freeing much of it again. The only thing we are rewriting though are some indexes, so no idea why this happens.