Just wanted to update this thread now that we nailed down what the issue was via email correspondence.
In the event any other users come across this kind of issue, make sure to check out some of the typed out info in your columns. In this instance, if you have a full URL typed out in a column, some email programs will try to display the full URL on a single text line, forcing the formatting of the rest of the email to accommodate it. To work around this, your best option would be to have some text or an image be linked to the URL instead.
As an example, if I typed out https://community.constantcontact.com/t5/Get-Help/bd-p/advanced_support in a multi-column setup, some email programs would end up trying to have it all fit on a single line, resizing all that row's columns. Instead, I can put "Click here to check our Community's general support page," and it would fit within the column settings as originally set.
Some email programs use different systems to render emails, which is what can cause the confusing discrepancy between email programs' displays in this particular instance. This can cause some differences in how even basic elements of an email is able to be displayed. For more info on these differences and how best to accommodate them, I'd recommend checking out this Community article.
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William A
Community & Social Media Support