The best replacement for pop3 is imap.

The best alternatives to pop3 are rated as following:
★★★★★  imap
★★★★  smtp
★★★  imap4
★★  hosted exchange
★★  exchange
★  http
★  imap outlook
★  pop
★  imap gmail
★  exchange server
★  imap server
★  webmail
★  forwarding
★  imap email
  imap better
  imap mail server
  smtp server
  imap hotmail
  mapi
  imap4 gmail
  pop3s
  imap account
  impa
  ms exchange
  imap wiki

Your alternative for pop3 is not listed? Suggest!
Speaking about pop3, one probably shouldn't forget about outlook com.

Other search terms related to pop3 and their ratings are:
★★★★★ outlook com
★★★ exchange server
★★★ exchange 2007
★★★ windows mail
You have in mind a companion for pop3 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of pop3 in all years. Click on graph for more.
pop3
imap
smtp