What websites should we use to test our content and deliverability?
mxtoolbox.com: insert the URL and click “Find Problems” - check for IP and URL blacklists (don’t be alarmed some are irrelevant)
mail-tester.com: send your copy with signature to check any possible issues then refresh the page
gmass.com/inbox: copy the email addresses and send an email that you are planning to send then refresh the page to get a proxy on if your are “inboxing”
Any issues in 2/3 require adjustments to content/signature