Yes, the Brand Indicators for Message Identification (BIMI) standard is quite specific about the logo's aspect ratio. The clear and firm requirement is that your logo must be a square, with a 1:1 aspect ratio. This is a foundational step for setting up BIMI correctly.
Getting this wrong can prevent your logo from being displayed, even if all your other DNS records like DMARC are configured perfectly. It's a simple but critical detail.
The reason for the strict 1:1 aspect ratio requirement is consistency across different email clients. Your logo will be displayed in various contexts and shapes; some providers use a circle, others a rounded square, and some a regular square. By starting with a perfectly square image, you ensure that your logo can be gracefully cropped or masked into these different shapes without being distorted or having important elements cut off.
The logo should also be centered within the square canvas for this same reason. Because the file format used is SVG (Scalable Vector Graphics), the actual pixel dimensions are less important than the ratio itself, as the image can scale without losing quality. The primary goal is to provide a single, versatile file that works everywhere.
Beyond the aspect ratio, there are several other technical specifications your logo must meet to be compliant with BIMI. Failing to adhere to these can also result in your logo not being displayed.
In summary, while creating a square version of your logo is the most visible requirement, it's just one piece of the puzzle. Adhering to all the technical SVG specifications is crucial for a successful BIMI implementation that enhances your brand's visibility and trust in the inbox.