Currently the Email deliverabiltiy via FLG can be quite viarable. I've checked all the Email deliverability best practices from FLG, but this still doesn't solve it. I think it's maily due to the fact that a masked email is used.
What would be good, and osome ther CRMs do, is to allow a plugin for Gmail accounts to be used for the sending. It could allow the records to be synced via Gmail and FLG - that way the email will not be masked, and the email sending will be delivered better.
FLG alread has a similar feature with the 'lead dropbox' so this could be leveraged with a plugin to provide a more integrated and automated experience.
I can share some screenshots with idease if you like, but don't want to share competitor systems on this forum out of respect!