There is no doubt that troubleshooting email design is very tricky. With the rising art of Chrome Dev Tool it makes deugging web pages and client side code very easy as we are able to see exactly what is happening. 

The main problem as email don't live in the web and also they need to go through a pre-processor before they go into a customer inbox. This makes it very difficult as sometimes oyu never know what is going to come out on the other end as you send a new email. 

Once way to combat this is to use an Email Code Validator. These are online tools similar to a Linter Tool to check for known bugs or attributes that are no longer in use. This is helpful as while we can't directly see in the Dev Tools what is not working properly we can see if a piece of code is buggy and change to a better support piece of code. For something like this I like to use HTML Email Check but there is an additional step to using this tool properly as HubSpot Emails are in a drag and drop builder and not raw HTMl. 

Step By Step:

1. Open your email in HubSpot and Click on the Preview Button
2. Click and Hold Down CMD + Opt + U (This opens the source of the email)
3. Click CMD + A to select all of the text and then CMD + C to copy
4.  Once you have this it's as easy as going back to HTML Email Check and then pasting in this raw code into the checker and hitting run.