The best replacement for microsoft outlook is outlook express.

The best alternatives to microsoft outlook are rated as following:
★★★★★  outlook express
★★★  lotus notes
★★★  windows live mail
★★★  seamonkey
★★★  evolution
★★★  thunderbird
★★  windows mail
★  express
★  mac mail
★  microsoft outlook express
★  mozilla thunderbird
★  live mail
  microsoft outlook web access
  apple mail
  google calendar
  yahoo mail
  microsoft exchange
  windows live
  ibm lotus notes

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

Other search terms related to microsoft outlook and their ratings are:

★★★★★ gmail
★★★★ yahoo mail
★★★ hotmail
multiple email accounts
hotmail account
google apps
You have in mind a companion for microsoft outlook and it is not yet here? Propose!

Google Trends

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microsoft outlook
outlook express
lotus notes