As much as it was rough in places (debugging an object oriented LotusScript library, connecting to a web service or dealing with a locked out 64GB NSF), I had to admire the email client was fully built as a Notes database and you could see all the source code for yourself so internally Lotus at least believed in it.

Having said that, once you're locked in (and I don't just mean email I mean the hundreds of custom applications your company has built) it's a slog to get off. Meanwhile you still pay the full licence costs whether you have one custom app or a hundred.