Missing mailbox folders

Hi BeauCosmo,

We recommend that you try removing and re-adding your mail account to see if the missing email boxes reappear.

Add and remove email accounts on iPhone - Apple Support

Add an email account

You can add one or more email accounts to the Mail app  so that you can receive all your email in one place and easily send email from any of your accounts.

1. Go to Settings  > Mail.

2. Tap Accounts, then tap Add Account.

3. Tap the email service you want to use—for example, iCloud or Microsoft Exchange—then enter your email account information.

If your email service isn’t listed, tap Other, tap Add Mail Account, then enter your email account information.

Note: If you set up multiple accounts, you can choose which account you want to send from when composing your email message. See Send email in Mail on iPhone.

Delete an email account

You can remove an email account from the Mail app  and from all the apps that use it on your iPhone.

Note: This action doesn’t cancel the email account; it just removes it from your iPhone. To close the account completely, visit your email account provider.

1. Go to Settings  > Mail > Accounts.

2. Tap the email account you want to remove from your iPhone, then tap Sign Out or Delete Account.

3. Note: If you change your mind later, you can add the email account back to your iPhone. See Add an email account.

We recommend the steps above because they can potentially resolve your issue.

Please let us know the outcome after giving the above steps a try.

Thanks for using the Apple Support Communities.

Cheers!