On a F5 APM for webportal, i changed the rewrite profile in order to:
all uri like ://.mydomain.com:/: rewrite
other (external uri) : not rewrited
so in the profile i activated split and put the scheme uri on the rewrite list
and empty on the Bypass list.
All loooks good (for exemple test.mydomain.com : rewrite) and twitter.com : not rewrite.
from this portal, i go to a webmail appliation (outlook through other LB F5) and in a test mail has two links: one inside the domain and a public (twitter) : For this two links, nothing is rewritten.
I only saw a difference which is 'xxx/owa/redir.aspx?xxxx'
So i think but i m not an expert :-) that once int he webmail application, the redirect exit the webportal and thus no rewrite.
solved : the problem was only that i did not use the fqdn but the ip address in my test...