Sending this text over Jabber:
Billing
   DNS Admin
   CacheNetworks LLC
   dnsadmin@cachenetworks.com
   2002 W Chicago Ave
   Chicago, IL 60622 US
   +1.1111111111

leads to sending this xhtml:
<html xmlns='http://jabber.org/protocol/xhtml-im'><body xmlns='http://www.w3.org/1999/xhtml'> Billing<br xmlns='http://www.w3.org/1999/xhtml'/>   DNS Admin<br xmlns='http://www.w3.org/1999/xhtml'/>   CacheNetworks LLC<br xmlns='http://www.w3.org/1999/xhtml'/>   dnsadmin@cachenetworks.com<br xmlns='http://www.w3.org/1999/xhtml'/>   2002 W Chicago Ave<br xmlns='http://www.w3.org/1999/xhtml'/>   Chicago, IL 60622 US<br xmlns='http://www.w3.org/1999/xhtml'/>   +1.1111111111<br xmlns='http://www.w3.org/1999/xhtml'/><br xmlns='http://www.w3.org/1999/xhtml'/> </body></html>

which is then converted by gaim_markup_linkfy() in serv_got_im() to:
<html xmlns='http://jabber.org/protocol/xhtml-im'><body xmlns='http://www.w3.org/1999/xhtml'> Billing<br xmlns='http://www.w3.org/1999/xhtml'/>   DNS Admin<br xmlns='http://www.w3.org/1999/xhtml'/>   CacheNetworks LLC<br xmlns='http://www.w3.org/1999/xhtml'/>   <A HREF="mailto:dnsadmin@cachenetworks.com">dnsadmin@cachenetworks.com</A><br xmlns='<A HREF="http://www.w3.org/1999/xhtml">http://www.w3.org/1999/xhtml</A>'/>   2002 W Chicago Ave<br xmlns='http://www.w3.org/1999/xhtml'/>   Chicago, IL 60622 US<br xmlns='http://www.w3.org/1999/xhtml'/>   +1.1111111111<br xmlns='http://www.w3.org/1999/xhtml'/><br xmlns='http://www.w3.org/1999/xhtml'/></body></html>

Note the bolded area -- one of the xmlns tags got linkified and is therefore highly invalid.

I'm not sure what the solution is for Gaim... I don't want gaim_markup_linkify() running at all on messages being passed to Adium, and I just noticed this because a patch to keep it from being called wasn't applied to our libgaim build.

-Evan