Hope someone can help. When in of the users is sending an attachment .xls from outlook it is not received by certain other outside people. I can receive it locally. I have checked her format is HTML have re-installed outlook, but it just won't go to those three users. They have received it from her before, this is what’s making it confusing.

Hello Lyanne Welcome to PCHF

If I understand correctly, you have 3 people that you can not send Excel attachments to? You can send .xls attachments to other people and they can open them just fine, just not the certain three people?

Can those three people receive any other type of attachments, just not .xls ones?

Can they open .xls attachments that other people send them?

Let me know and we can go from there.