Mailing lists and attachments

[Kian Karas <kian karas dev gmail com>]

I'm new on GNOME mailing lists (and mailman in general) and I made a post where I included an attachment. The attachment (a 21 kB PNG image) did not show up in my post:

https://mail.gnome.org/archives/gtk-app-devel-list/2018-January/msg00019.html

Is it not possible to include small attachments? Did I do it wrong, or should I have uploaded it to a service and included a link instead? What's the normal procedure?

I realize this is a noob question that I should be able to find somewhere, but I'm sorry to say that I have not been able to do so.

Thanks