Due to the challenges to detect and filter phishing emails, it is inevitable that some phishing emails can still reach a user's inbox. As a result, email providers such as Gmail have implemented phishing warnings to help users to better recognize phishing attempts. Existing research has primarily focused on phishing warnings for sighted users and yet it is not well understood how people with visual impairments interact with phishing emails and warnings. In this paper, we worked with a group of users (N=41) with visual impairments to study the effectiveness of existing warnings and explore more inclusive designs (using Gmail warning designs as a baseline for comparison). We took a multipronged approach including an exploratory study (to understand the challenges faced by users), user-in-the-loop design and prototyping, and the main study (to assess the impact of design choices). Our results show that users with visual impairments often miss existing Gmail warnings because the current design (e.g., warning position, HTML tags used) does not match well with screen reader users' reading habits. The inconsistencies of the warnings (e.g., across the Standard and HTML view) also create obstacles to users. We show that an inclusive design (combining audio warning, shortcut key, and warning page overlay) can effectively increase the warning noticeability. Based on our results, we make a number of recommendations to email providers.