whenever I reply or compose a new email in Thunderbird, my personal account sends the email my default. I want to make it so that my school account is the default, but I don't know how to set that. Does anyone have any idea on how to fix it? I'm sure I'm just missing a button or box to check.
Thanks all!
The previous two replies don't answer what Ryan wanted to know. There is a difference between default SMTP account and default email account.
If you want to change what email address is preselected when composing a new message, you need to change the default email account:
Source: https://getsatisfaction.com/mozilla_messaging/topics/how_do_you_set_default_account
Note: As Ryan noted in this comment, the preselected address also depends on what folder is currently displayed. Though if you're not currently in a folder linked to a specific account (e.g. unified inbox), the default account is preselected.
In Thunderbird, go to EDIT, ACCOUNT SETTINGS. Go to the bottom left and Select OUTGOING SERVER (SMTP). Click add to add your wanted server if it's not in the list.
Next scroll back up and click on the account you want to modify. In the bottom right, select the outgoing server you want for that account.
You should set your school account SMTP server as the default. Go to Edit - Account Preferences, scroll down to Outgoing Server (SMTP), choose the one you want and set it as Default.
Whenever you send an email it will be sent by that SMTP server