When sending or receiving e-mail messages always take into account the following:

Some mail server from other domains may enforce other size limits (eg. 8MB). For that reason it is recommended to keep e-mail attachements as small as possible (e.g. by compressing them to a zip file) or to make files available in an other way.

More info below the header: Exchanging files.

Save or open attachments

More info can be found here: Open or save e-mail attachments