Christiane_Rode

As @Darshil_Shah1 linked, the status page can be helpful. I'd also recommend signing up for email notifications. A lot of times, I'm notified via email before I experience the issue.

Can you see anything similar about their inferred information (I know you mentioned a lot that wasn't similar)? If you have city/state/zip on your form, does it match the inferred information? Are they using VPNs to hide who they are? To be clear, VPNs are incredibly common, especially in the remote...

Something to keep in mind when you're looking at Bot Activity Opens, in my experience, the filter (or the log) hasn't caught opens as a result of image prefetching. So, for example, opens that are likely the result of Mail Privacy Protection will still make it through with a bot activity label of "F...

That's definitely something to check -- editing certain parts of the code in the email itself (and not in the template in Design Studio) will cause your email to break from its template, and modules will no longer be editable. More info is available in the section "Breaking an email from its templa...

Are you able to send over any of the HTML for the body content of your email? I think it would be helpful to see how your container and modules are set up in the body and see if there are issues there. Also, not sure if you have this bookmarked, but I find the Email Syntax guide to be helpful.

Are there any similar characteristics between folks who engaged in the earlier timeframe and those that dropped off in the second? If you open the click activity for some of those identified users, is there anything there that's similar among them (browser, device)?

As @Darshil_Shah1 said, definitely check with your admin on whether or not you're using filtering or logging bot activity. Also, be cautious with CTO -- as opens can be unreliable due to MPP or image prefetching, you could be factoring in opens from people who never truly opened your email. Some t...

What does it look like when you preview the emails in email clients? The web view in Marketo often does not match the inbox rendering (especially Outlook, which can have its own issues with supporting padding) -- are you seeing this issue with your test emails?

We were weighing these tools from more of a deliverability evaluation standpoint (not necessarily gauging opens or post-send success metrics, given we want to move away from using that as a success metric, so my research might not match what you are looking for). But we looked at Litmus and Email on...

As @Vinay_Kumar a snippet is helpful for future planning. Also consider a MyToken depending on what your needs are.