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I read my email on my phone. I rarely (read: never) use Cox's webmail as it's simply not a good format for mobile mail.
I use the Gmail app on my phone to read and send email, however, Cox doesn't send the Spam or Junk folders. I have several Cox email accounts and every one of them exhibits this behavior - no spam or junk folder.
This is on a clean and fresh installation of the Gmail app on a new Galaxy S21 Android phone.
I have gone to the webmail settings and made sure that Spam/Junk is marked as Subscribed in the IMAP settings.
This is only important because sometimes email is delivered to Spam/Junk by mistake and I have no way to check those folders.
How do we fix this?
You were already publishing these folders from Cox webmail before the clean/fresh install on your Galaxy?
Can you see these folders if you use a web browser for GMail?
No... because Gmail on the web only accesses gmail accounts, therefore it is impossible to use Gmail on the web browser to access a Cox account. The mobile app works with any POP or IMAP account.
When I use the Gmail app on my phone to access Gail accounts I can, of course, access all the folders in the Gmail account.
The reason I use the Gmail app to access my Cox accounts, is because it's the only client I've found that works with Cox (mostly) reliably. Outlook and Thunderbird, for example, keep losing connection with the Cox servers. Support for both of those clients say the same thing - Cox removes the security token, which requires setting up the client servers again every time this happens.