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in irssi (when connected to a server, not on a channel):
/whois your_username
you will get smthg like "your_username@ isp.ip...........".
add that to /etc/hosts instead of hostname.domain.org
it should now look smthg like this:
127.0.0.1 your_username@ isp.ip.... localhost
reboot
it worked for me. special thanks to lavapunk :!:
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