This redefines “reaching across the aisle” :)

Same here. And, as someone father up this thread observed, forcing a big exodus in a short span of time is the Best possible way to bootstrap this migration :)

(The following is second-hand experience) You should google “DKIM and SPF” before you embark on this journey. The tl;dr of it is that senders of email can (and do) end up blacklisted based on the IP Address of their mail server. If you run your mail server on (say) a.b.c.xx and a known spammer happens to rent a vps from the same provider at a.b.c.yy, you both end up blacklisted. The spammer moves on, whereas your emails fail t make it through other folks’ spam filters, and there won’t be anything you can do about it.