ppo @kylotan
I had some luck with the following trick for those stubborn SMTP servers that don't respect TTL values.
Create the following email address at OS:
migrating@username.opalstacked.com or
migrating@app.username.opalstacked.com
Change the forwarding address, via the WF CP, to that "migrating" email address.
Since you can control what WF's incoming mail server does, when new mail is errantly delivered to it, you'll get it at your new OS Mail User or wherever you want it to go via the OS CP.
Using @username.opalstacked.com is helpful because it also avoids any other DNS propagation issues that might arise with the domain name you're also in the process of migrating.
I realize this solution isn't going to be great if you have many email addresses. But maybe it'll help if you only have a few.
