Can I trust rumbo.es? Help me!

You should probably think of these things before sending an e-mail off, but here are three points to ponder: (1) E-mail is not confidential or secure – people send credit card details this way all the time and have never had their data compromised, but technically, it is absolutely not secure in any way, shape, or form. (2) Entering these details on a secure website is preferred and is about as secure as you can be. Still, nobody can guarantee absolute security, no matter how secure their system is. (3) When completing transactions on websites, look for https in the address field (s = secure), a padlock icon, a security certificate, or some other indication that the processes they're using are secure. Since you've already sent this information via e-mail, there's not a lot you can do with this particular transaction. Playing the odds, you'll probably be okay as this appears to be a reputable organization. Since you used a credit card, at least you'll have some protections should something be compromised/someone uses your card number to make huge purchases without authority.

thanks a lot. i looked at the official of the aircompany and my ticket was already saved, so i think i can trust the site.

This is for a plane ticket, right? The airlline must need this information. As far as trusting rumbo.es, I will say that I have complete confidence in them. I bought several train tickets from them, before I could get my credit card to work on the Spanish train site, renfe. On the second purchase, they provided the ticket (which I could print out at home) before my bank actually approved the charge. My bank then rejected it, so they emailed me (from the email address you listed) and politely asked my to contact my bank to authorize the charge. I did, and wrote back to ask them to put the charge through again. I got a prompt response thanking me for my help.