If a mailbox is not constantly emptied, overly large attachments can clog it and prevent the owner from getting email.
Ask Before You Send Huge Attachments
This is why you should
- ask before if it's okay to send a larger file (>1 MB) via email,
- compress whenever it makes sense and
- send a small version of any image before sending the full-resolution picture.
As an alternative to attaching, you can use file sending service, which can deliver files GBs in size.