I can't find anywhere to specify which email address Lightning uses to send the accept email.

The one you assigned to the calendar.

Pending outbound mail is usually found in the Outbox under Local Folders. Have you checked there.

Sorry that I know so little about Lightning, but I created my calendar a long time ago and I haven't used it much. When I created my calendar, I had entered an email address that now can no longer send messages. So tonight I created a new calendar that sends notifications using a server that works. Can I change the email address for my previous calendar? If not, how do I copy an event from my old calendar to my new calendar? And will this allow me to send another Accept email?

I tried copying and pasting the event from my old calendar to my new calendar, but I ended up creating a second copy in my old calendar. Then Lightning asked me if I wanted to send a notification email. Would this notification email be the Accept email that I'm trying to send, or would it try to invite the other people who are already invited to this meeting?

Thanks for bearing with some beginner questions!

Pending outbound mail is usually found in the Outbox under Local Folders. Have you checked there.

There are two folder under Local Folders: Trash and Outbox. Alas, both these Trash and Outbox folders are empty. Maybe I need a particular setting to get messages stored in the Outbox folder when the SMTP server doesn't work.

Do you have the calendar list showing on the left margin of the calender page? If not from the menu bar select View-Calendar-Calender List You need to be in the calendar window when doing this. If the list does not show but the option in the View menu is checked, move your mouse to the left margin and watch for the cursor to change to a double header arrow. When it does left click, hold and drag to the right to uncover the list. Now you can double click the different calendars in the list to open the edit dialog box for that calendar. You can also double click any event to open the edit dialog box for that event and move it to a different calendar.

Right-click the troubled calendar in the list on the left - Properties. Select a working email account from the 'E-Mail' drop-down menu.

Bingo! When I double-clicked on my old calendar, the edit dialog box let me change the email account used for that calendar. I changed the email account for my old calendar to an email account that could send emails. Then the status of my event was changed to "I will confirm later". When I changed the status of this event to "Confirmed", Lightning asked if I wanted to send out a confirmation message. I said Yes, and I think that I am now confirmed for my meeting!

I never did see how to move an event from one calendar to another, but now that I fixed my old calendar, I don't need my new calendar.

Thank you so much!

The last line in my previous post tells you now to move an event.

"...You can also double click any event to open the edit dialog box for that event and move it to a different calendar."

When I double-click on this event, I see a pop-up form with the following fields: Title, Start Date, End Date, Location, Organizer, Status (Confirmed), Reply (I will attend), Reminder (No reminder), Attendees, Description. The two buttons on the bottom are OK and Cancel. Perhaps I'm missing a setting on one of my calendars that I set up that allows me to move from the old calendar to the new calendar.

Do you see a field for Calendar like the one I outlined in the attached image?

When I double-click on an event to display the properties for that event, the image attached below is an example of what I see. Although the image you attached in your message is really fuzzy, my example looks different. I don't see a Calendar field in my example properties form. I don't think I'm displaying the same form as you. How did you display your form?