If my customer loses the confirmation email, can they get their ticket or voucher sent again?

Yes, a lost confirmation is one of the easier problems to fix, because the portal keeps the booking and its documents after the email has gone out. You can open the booking in your admin area, find the ticket or the hotel voucher against it, and send it again to the same address or to a different one if your customer has given you a new email.

Most portals also let your customer help themselves. If they signed in when they booked, the trip sits in their account and they can download the document from there. If they booked as a guest, there is usually a page where they enter the booking reference and the email address they used, and the portal shows the trip and lets them print it. Which of these two routes you have on your own site depends on how your portal has been set up, so it is worth trying it once yourself so you know what to tell people.

There are a couple of honest limits. The portal can only resend what the supplier has already given it, so if a ticket was never issued or a voucher never came back from the hotel, resending will not produce one and the booking needs to be looked at properly instead. Emails can also land in a junk folder or be blocked by a company mail system, so a resend that appears to work may still not arrive, and in that case sending it to a personal address usually gets through.

The next time this comes up, check the booking in your admin area first to confirm the document is really there, then resend it and ask your customer to look in their junk folder as well as their inbox.