I am unclear on your problem, as Thunderbird has no realistic limit on attachments. What error messages are you receiving?

When I select the three images I want to send, only one lights up. Perhaps it's a problem with my computer? But I never had this problem with Outlook.

Try adding one at a time and see if that works.

Good suggestion, but it still only takes one image. This is a feature that Thunderbird needs to improve.

It's very time inefficient to have to send three photos in three separate emails.

I meant to click to add each photo separately into one email.

Before announcing what needs to be improved, I encourage you to spend a few months using it. Thunderbird has millions of daily users.

I will add that I, and most users, can click as many photos as desired to be added at once. There may be a problem with your setup.

I too have this problem. In Outlook, I could select 10 messages and insert or attach them with no issue. With TBird, I can only select ONE at a time. I select the first one, move the cursor over a few spaces (so the first image doesn't get overwritten), then go fetch the second one. Even for only 2 photos, it takes time. Imagine 20 photos you want to share with someone who has email only, no Facebook, no Dropbox.

I have attached several files to an e-mail message in one step using each of three methods:

1. Start a new message, select several files on my desktop, and drag them onto the new message.
2. Start a new message, click "Attach" in the toolbar, select several files in the window that appears, click on "Open".
3. Start a new message, use the keyboard shortcut for "attach" (command-shift-a on Macintosh, probably control-shift-a on Windows), select several files in the window that appears, click on "Open".

These methods can also be combined: drag some files onto the message, select others from windows.

Is one or more of these methods not working for you?

Bob, I'm sorry that I don't understand "I select the first one, move the cursor over a few spaces (so the first image doesn't get overwritten), then go fetch the second one." I'm not aware of any need to move a cursor (what are "a few spaces"? do you mean the mouse pointer?) or to be worried about overwriting a file. What are you doing to "go fetch" another file?