Some Xfinity emails not syncing to Apple Mail via IMAP

Some Xfinity emails not syncing to Apple Mail via IMAP

I am having a selective IMAP synchronization problem with my Comcast.net email account on an iPhone using Apple Mail.

Ordinary email synchronizes correctly. However, some bulk/subscription emails appear in both Xfinity Webmail and Outlook on my Windows PC but do not appear anywhere in Apple Mail on my iPhone. This occurs with messages from more than one sender and more than one bulk-mail service.

The missing messages I checked all contain this Xfinity header:

X-Xfinity-CCat: promotional

An ordinary personal email that synchronizes correctly does not have that header.

As a test, I forwarded one of the missing messages to myself. The forwarded copy appeared on the iPhone almost immediately, while the original remains absent.

The iPhone account is configured for IMAP using imap.comcast.net, and ordinary messages synchronize correctly. Apple Mail is also set to List View, so this is not simply a Categories/Promotions display issue.

Could an Xfinity email specialist investigate whether messages classified as X-Xfinity-CCat: promotional are being handled differently by the IMAP server?