Gmail can be accessed through various ways you aren't stuck with the web page.
For a business especially consider getting your own domain which would likely give you multiple email addresses on it for a few $ per year and be completely unaffected by changes in your internet.
It would look more professional and easier to give out and remember - like Tony (at) xxxfarm.com or office (at) xxxfarm.com
You certainly don't want anything tied to a specific ISP which they hope acts as leverage to keep you with them.