You can attach multiple files to an email in two different ways:
- When selecting the files to attach, select the first file, hold down control on your device, and select the other documents you would like to attach.
2. The other way is to use drag & drop from the file directory, directly in to the composer.
The size limit of the attachments is less than 25MB (per email), and the total number of files that can be attached is 100.
These limits are both for sending and receiving messages, and apply to all ProtonMail plans, including the Free plan.