Hi Babu,
You could save it on Portal as web file, because it has public visibility.
1. Create a web file record, set Parent Page to Home,
then we can visit the image via portal Url/Partial Url
e.g: xxx.powerappsportals.com/company-logo

2. Upload company logo as note file:

3. Publish the web file:

4. Check whether our logo is available after publish:

5. Add it to img element in HTML file

6. Select whole image by cursor, press ctrl + c to copy element.

7. Paste it to content of sending email step by ctrl + v

Result: everything is same:
we can find company logo URL and its attached link by inspector.

In addition, you could modify width and height attribute of img to get a proper size for logo.
Regards,
Clofly