Doesn't seem to work if you are using a combination of BES and BIS

Been using 4.5 for a week or so on a 8800 on o2 and activated BIS before I did my BES activation.
Just tried requesting the servicebooks from o2 which appeared to come through but no HTML email on the inbound from yahoo email address.
Does the BES server take precedent over the BIS for email settings?