Hello @YasirT1 ,
So for how the email is received depends on the email client that is being sent to. The best way for you to preview what your email will look like is within the email editor in the top right hand corner you should have a drop down button saying, ‘check and preview’ select preview to look at it from a desktop view as well as mobile rendering. You could also always send yourself a test to check it within the email client directly.
For your contact upload related question you could go a few different ways. You could export all your contacts onto a excel file and then upload from a file into Constant Contact. The other option is we have an integration with Salesforce that once the connection between the two systems is made you contacts will import automatically into Constant Contact. Below I have attached an article that goes over the manual import process from Salesforce. As well as the link to the marketplace; where you can find all third party integration options.
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