Reference (but it’s vague): http://www.afternet.org/help/connecting/ssl
NOTE: AfterNET is adding a wildcard SSL certificate. This may obsolete these instructions.
1. Download the certificate.
2. Create a folder afternet.org
under /usr/local/share/ca-certificates/
3. Copy afternet.cer
to /usr/local/share/ca-certificates/afternet.org/
4. Symlink it as 90511bdb.0
5. run update-ca-certificates
to update the certificates list.
6. Open x-chat.
7. Edit your AfterNET entry.
8. Remove all the old servers and instead add.
9. Check both Use SSL for all Servers on this Network and Accept invalid SSL certificate.
Done.