Send box

I'm amateur photographer and I work with lightroom CC 2015. When I want to send my pictures, I use my raw files instead Jpeg.

Now I have a problem with my Mail send box. I tried to send my files from lightroom to my friends, but the apple Mail send box stayed jammed on the mail I want to send.

I tried to quit Mail box several times and come back to it, but I always have the same picture of my send box, jammed on the mail I want to send.

I have stoped my iMac for one week, because I was working outside my country and when I came back, before starting my computer, I restarted my router. Then I restart my iMac and when I opened the Mail box it was still the same that one week ago.

Finally, I disconnected my gmail and iCloud drive count but when I reinstalled it it was the same.

It's a big problem for me because I don't want to reboot my computer for this, I would like to find a better solution.

Could you help me ?

Thank you