In Office 365 for business, it's easy to share files with people in your organization, but sometimes you will also need to share with people outside your organization. To share files securely with your customers, you can send a secure link.
At the top of the Documents library on your SharePoint site, click New, and then select Folder.
Give the folder a name, and then click Create.
Upload the files you want to share to the new library, or choose New to create new documents directly in the library.
Select your new folder in the Documents library, and then click the Share button.
In the Send Link window, click the list at the top, choose Specific people, select Allow editing, and then choose Apply.
In the Send Link window, enter your customer's email address, type a message, and choose Send.
Your customer will receive an email with a verification code, which they'll need to send to themselves to access your folder. If they can't find the email, they should check their Spam folder.
To share files securely with your customers, use a secure link.
In the Documents library on your SharePoint site, create a new folder. Then add the files you want to share and work on with your customer. You can create them here, or upload them from your computer.
When finished, return to the folder you created, and then select the Share button.
For the people you want to share with, choose Specific people, then Allow editing, so they can edit the document. And Apply.
Now type your customer's email address and include a message for them. Then, Send.
Your customer will receive an email. If they can't find it, they should check their Spam folder.
In the email message, they'll see a link to the shared folder. This takes them to a SharePoint page where they're asked to send a code to themselves. Select Send Code, and then return to the Inbox. Again, if the email doesn't show up, check the Spam folder.
Open the email and copy the verification code. Return to the SharePoint page and paste it in. Then, select Verify.
Your customer can now see and edit the files you shared with them. You can work on these files together, add more files, or download files for the duration of the project.