Mailing Mac lotus notes 8.5 documents Problem

Hello there.
Can you please help me.
Some user are using “Mac lotus notes 8.5” or 7, and send out attachment documents to “yahoo/gmail” a xls or doc files,
the “yahoo/gmail” says “it is virus Can’t open”.
If the same file send from “XP client 7” or 8, there's no problem.
What should i do or change the setup in Mac to make it okay?
Please help and thanks a lot.
God bless.
