Improving deliverability isn't a one-time task; it requires ongoing monitoring. Keep an eye on key metrics that reflect your deliverability:
Bounce Rate: This is the percentage of emails that are not delivered (rejected). A high bounce rate (especially high hard bounces for non-existent addresses) is a warning sign. If you see it increasing, stop and investigate: perhaps a list has become obsolete or you have a collection of lists that have not been validated. Consistently high bounce rates will degrade your reputation, so you want this number to be as low as possible (usually under 2% for hard bounces is a common benchmark, although lower is better).
Spam Complaint Rate: Most ESPs will show you how many recipients marked your email as spam (if you have feedback loops integrated). This percentage should be extremely low (ideally well under 0.1% per campaign). If you see chiropractor email address a spike, analyze that send: were you sending to older addresses? Did the content or subject line trigger people? Even a small number of complaints is very damaging, so always try to minimize it by following the best practices above (permission-based list, easy opt-out, relevant content).
Open and Click Rates: While open rates are becoming harder to measure accurately (due to privacy changes), they still give a directional idea of engagement. A declining open rate over time could mean more emails are going to spam or being ignored. High open and click rates are a sign of a healthy email program and also indicate good deliverability (emails in the inbox tend to get opened more). Positive engagement like opens/clicks “improve your chances of inbox placement for future sends.” If you use tools that directly measure inbox placement (some services can tell you what percentage of emails went to inbox vs. spam for seed accounts), track those reports as well.