On a new VPS (or you've run '/scripts/upcp' to update cPanel), you login to Squirrelmail and hit this error:

ERROR: Connection dropped by IMAP server

Courier-IMAP is linked against libfam, and that library is probably missing. Use SSH for the following.

How to Check

[email protected]#  ldd /usr/lib/courier-imap/bin/imapd
libfam.so.0 => not found
libgdbm.so.2 => /usr/lib64/libgdbm.so.2 (0x0000002a9566c000)
libcourierauth.so.0 => /usr/lib64/courier-authlib/libcourierauth.so.0 (0x0000002a95772000)
libc.so.6 => /lib64/tls/libc.so.6 (0x0000002a9587c000)
/lib64/ld-linux-x86-64.so.2 (0x0000002a95556000)

How to Fix

[email protected]# yum install gamin