SOLVED
(You should use inline images, not attachments; not all Jive clients can even see the attachments.)
Thank you, so with the way the flow is set up, according to your recommendation for the trigger, I should be able to track and store the CSV style like your example above?
You can check that quite easily: as you run people through the flow, that history field should be appended to in a consistent CSV-type fashion. You can look at the value right in the Marketo UI.
Will that history be included on the alert email that goes to our sales team? Or since our CRM is not integrated I am still only limited to last interesting moment. I believe that is what was said previously.
I think you're still confused. 
When you use a Textarea as a history field, as Dan shows you how to do, you're updating a standard lead field (which you could output exactly as-is with the corresponding {{lead.token}}). Calling it a "history field" gives it a clear purpose in your environment (it tells you that you should be appending to it, not overwriting it, at least for the most part) but in all other respects it's just like any Textarea.
Consistently structuring the contents of a history field is a good idea if you ever want to machine-parse that history field using Velocity token, or even if you want to extract your entire Marketo database and parse it offline using any other language. Technically, datetime - colon - activity type - comma - activity details - linebreak is also "consistent," but it's not a well-known structure, so better to stick with the tried-and-true-er CSV. (Or if you're really adventurous, use a JSON format, which is even better for machine parsing but gets hard to read for people.)
Simply having the history field in a parseable format doesn't mean it automatically gets parsed, though.
If you only output the {{lead.History Field}} token in an email, no parsing of any kind happens.
If you have a Velocity {{my.token}} and it only contains the one line of VTL code ${lead.History Field} then similarly, no parsing happens (since you're in Velocity, you're able to parse it before printing, but you're just printing it instead in this case).
To take advantage of how Velocity can parse and filter in a CSV-like field, well, you actually have to parse it. That is, split on the line breaks and split on the commas to create "live" Velocity objects. Then you can do things like re-sort by type of activity, filter by form name, etc.
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