How can I log in to ICQ using Messages? It used to be possible to log in to ICQ accounts with iChat by using your ICQ login info as an AIM account. However, that functionality seems to have been removed - if memory serves, with the introduction of Lion.

Is there any way to use ICQ with Messages under Mountain Lion?
Setting Server to login.icq.com and Port to 5190, unchecking SSL in Server Settings tab should help.

Add:

Enter only the first eight characters of your password, leaving off any extras.  This consistently worked for me.  I use OSX 10.9 Mavericks and Messages.

Some have had results leaving the last character off their password.