Am I making a mountain out of a molehole?

I just want to know if I'm being too untrustful or not. My hubby works an hour and a half away for a company that's based 4 hours away. There is a secretary at the base who does his expence reports and the like. I know they chit-chat and he says it's "completely professional", but I have my doubts. Why? Because we met up with the "base people" and had a closing dinner. She was the only one he didn't introduce me to. I had to ask him to introduce us. And she avoided him all night. That's fine, but when she did talk to us, she only looked at him. Then today I see that he deleted some "sent" emails to her. I'm just wondering, If this guy is saying he has nothing to hide and gets so upset when I bring it up, then why is he deleting his emails? Is something up or am I just blowing this way out porportion?