This is a bit of a complicated issue. The custom code email you are working with is all in XHTML, which requires the SimpleURLProperty to track links. This SimpleURLProperty tag isn't allowing the alt text to be viewable in Outlook. To fix this, we highly recommend not using XHTML, and switching to just HTML. HTML automatically tracks links, so you don't need the SimpleURLProperty.
We also recommend using height and width attributes, as well as filling in the alt text attribute between the quotations; having the set height and width attributes will allow Outlook to display the alt text attribute as intended.
If you do have more questions on HTML/Custom Code emails, give our support agents a call here! We have a special team that will handle any and all Custom Code template questions.
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