Emailing an Access database

I sent an Access db in Outlook to someone who needed it. They said they couldn’t open it, that they’re OS (MS XP) blocked access to a potentially unsafe attachment. Now they want me to change the “file format” of the DB to “txt, saying that once received, they would convert it to an mdb. I think they just need to be given rights to open it on their end. Pls advise. Thanks.