The phrase "postal mail" refers to a traditional way of sending letters or packages using a postal service. It means using the regular mail system instead of electronic or digital methods like email or messaging apps. Full definition
We send by postal mail, which means a real human carries it the whole way. (theyogaposter.com)
We do not accept submissions via postal mail, and we do not accept books on disk. (smashwords.com)
Unless you so request, any personal information that you provide in communications to the above e-mail and postal mail addresses will not be used to send you promotional materials. (nationaleczema.org)