Cant send email using wifi only using sprint

[Simpdapimp]

i can recieve messages into my sprint pcs account on my phone, but when i try to send a message it gives me an error. has anyone else encountered this problem. i first noticed it when i was trying to use the nuemms over my wifi and it wont send but when i do it over sprint cell service it works! i just realized that none of my other accounts will send over wifi either.