Exchange 2007: POP3 ERR Command is not valid in this state

Summary: POP applications report ERR "Command is not valid in this state" after supplying credentials. To verify you try telnetting to POP port 110 of your CAS server:

Telnet CASServer 110
User Myaccount
Pass Mypass
ERR Command is not valid in this state


Resolution: Open your Exchange Shell and enter:

Set-PopSettings -LoginType PlainTextLogin

Restart your POP3 service


James Chong (MVP)
MCITP | EMA; MCSE | M+, S+
Security+, Project+, ITIL
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