Please check the below link.

If you noted the footer in mobile screenshots, you can see that the address appears in red. But it is actually gray in color and appears as such in all email clients except iPhone(but 7 and 7s shows gray). Is there any method to fix it?

Note: When I removed the number from the address, it gets fixed automatically. So I think the issue issue is related with numbers.

(I am not sure if this issue is already resolved. But I couldn't find and exact solution by searching the community.)