When I got my phone several months ago, I was surprised to discover that there are few iPhone mail apps that support POP3 properly. I tried several apps and only the native Apple app and AltaMail would connect to my GoDaddy POP3 account. While its certainly possible that other clients may or may not work currently, Im glad that situation forced me into AltaMail. For me, this app has proven to be a real performer. Support and communication with the company has been very responsive as well. AltaMail is now my "go-to" mail application.
Rpm2hi about AltaMail Classic, v5.8.1