There is a way to get Gmail to deliver for sure! Open up one of the mis-filed messages that landed in spam. You can take the "spam" label off it, or select the "not spam" button, and that might do it. But the fool-proof trick is using filters.

To do that: select "More". Select "Filter messages like these". It'll start with just the from address filled in, which is usually perfect. Select "Create filter with this search". Then check "Never send it to spam" on the next screen, then "Create filter".