Email Deliverability Experts Needed for Klayvio Shop Client Issues

Hi All - does anyone specialize in working with Klayvio shops re: email deliverability? I have a client claiming 62% open rates (and very little engagement) form their email marketing. They are sending to known customers that already bought something in the past, this is not cold to strangers but rather warm to existing purchasers of vitamins and supplements (B2C and mostly personal email addresses). The customer current sends 100,000 person blasts from a single domain, in a single batch. I’m looking for someone that can: 1). Test current domain health 2). Has expert knowledge on tracking pixels that Klayvio uses to determine opens (are they fooled by Google or outlook or yahoo’s servers opening the email as opposed to the recipient opening email) 3). Recommend solutions to permanently fix issues found in health check of current email setup. If this is your area of expertise, please send me a DM with the following: 1). Are your email health tools proprietary or off the shelf? 2). Have your found errors and issues with Klayvio before? 3). Do you have strong ideas / suspicions of email health (being poor) based on the information shared? 4). What is the maximum number of emails sent per month for the Klayvio customer(s) you’ve worked with in the past? What my client is not looking for. -someone that “thinks they can do it”, but doesn’t have relevant experience they can articulate in similar situations. There might be a role for Clay to play in the solution. Thanks in advance for your consideration.