there is none bug in round cube , not in one webmail from ampps.com
check first what mailserver you run.
check your php.ini
check if your mailserver can sent mails treu port 25 (alot of providers blocked this port)
are your ports open for public?
if you install roundcub or whatever , for imap you can use localhost...
login with your emailadres and password it will work and sent emails ....
alot of people thinks that running servers is a easy think there is more than meets the eye hahah
----------------------- What i dont K'now must be born...
ON internet from 88/89 , working with computers from the year 1982 c64 , comodore , amiga and ect bbs