Paul has recently been talking about looking for new email clients and issues he has had losing emails when they are redirected. He mention it being related to going through multiple spam filters but I believe it may have more to do with DMARC policy settings that certain email providers have set. I had some issues with this a few years ago and could no longer redirect emails I received from people using Yahoo, AOL, and a few other email services. I was able to figure out a work around but that was specific to the email provider I was redirecting from. This was a few years ago so maybe something has happened in the mean time so this is no longer a problem but thought it was worth mentioning.