I've been asked to post my solution.
Problem: During my migrations from Gmail to Apple Mail to Postbox my folder structure went ballistic. Every migration caused my folders to go from the normal black text to light gray italics, no matter the application. Since my folder (label) structure is complex for this gmail account. Looking thru all of the labels to the left in my Gmail account wasn't an option. Many email clients consider these entities folders, but Gmail calls them labels.
- Rebuilding the inbox, folders, nor files in any application worked. I attempted this within both MacMail.app on OSX and Postbox.
- Folders were still grayed out. Creating new folders in these clients and moving the sub-folders around didn't work.
- After an hour of playing around trying to find the secret sauce, I opened my Gmail account and went to Settings->Labels.
- I noticed that many of the labels (sub-folders) were rooted incorrectly, which meant they had lost their parent account during my many migrations.
- I created new parent 'Labels' in Gmail and one-by-one moved the sub-labels underneath the parents by using the edit functionality.
- After moving around almost 100 labels in Gmail.
- I re-opened Postbox and removed that email account from Postbox.
- I closed Postbox and re-opened it.
- I re-added the email account to Postbox.
- And, that fixed everything.
PS - If anyone knows how to mass edit labels in Gmail. Please let me know.
-Brad