Hey Anne,
Thanks for the details. Based on what you’re trying to do (one mailbox, reply from the appropriate address, and drag messages into a single folder structure), you likely don’t need two separate domains.
A simpler option is to make the secondary domain a domain alias of the primary domain. That way, you keep one mailbox and can add a second From identity in webmail to send as either address. This also lets you keep all mail in one folder tree and drag messages wherever you want without forwarding and enables you to share these folders with other users on the same domain.
Kind regards,
Zach Sylvester
Software Developer
SmarterTools Inc.
www.smartertools.com