It looks like the recipient server is marking the emails from Intuit as SPAM as they are coming from an IP address that is listed on Blacklists. ie 167.89.58.229

Here is an extract from the header file;

"HeaderValue": [

        "MAILSPIKE-H2: \"trusted sender\"",

        "SORBS: \"Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?167.89.58.229\"",

        "BADWHOIS: This E-mail came from e.notification.intuit.com, and is listed in BADWHOIS.",

        "ENVMISMATCH: Env sender (bounces+2327135-5441-User.name=userorg.[email address removed]) From: ([email address removed]) mismatch.",

        "MESSNIFFER: Message failed MESSNIFFER: 53.",

        "MESSNIFFER-SCAMS: Message failed MESSNIFFER-SCAMS: 53.",

        "WEIGHT5: Weight of 54 reaches or exceeds the limit of 5.",

        "WEIGHT15: Weight of 54 reaches or exceeds the limit of 15.",

        "WEIGHT20: Weight of 54 reaches or exceeds the limit of 20."

I note that the IP address (167.89.58.229) is not on the list of Intuit addresses at https://quickbooks.intuit.com/learn-support/en-us/manage-intuit-account/unable-to-receive-intuit-ema...