You have created your email signature template with all the required information and images. Your first initial email looks correct, but in some cases when you reply or forward the email, the images appear very large or resize without knowing why, sound familiar?
This happens because some email clients (providers) ignore the Width and Height values set on the image(s) in the signature template and revert the image(s) back to the Native image size.
To prevent this issue from occurring, you will need to ensure that the images used within your signature design are created at the required size for the signature template.
For example, your logo is created at 1000px by 1000px but the signature template requires the logo to be 100px by 100px in size.
You can try to do this one of two ways:
Option one: Place your image in the email signature box, then place your mouse on the border of the image box to resize it within the email signature.
Now, instead of re-sizing the image in the signature template, create the image at the required size - you can use Image Editing applications, such as Photoshop or Paint.NET. You could also use an application like Preview on Mac to resize the image so its natural size is closer to what you would like. This would keep any other email provider from resizing the image in whatever they want.
Then upload the image to the signature template again.
For example, the original image is called "mylogo_original.png"; when you re-size the image then rename the image to "mylogo_100x100.png" - this allows you to identify the re-sized image quickly.