Question about automated email when a new record is created

re: My first question is, if I create a record but don't enter an email address quite yet, will Airtable send an email when I go back and enter an email address later?

Nope, it'll immediately attempt to send an email and will fail at that point.  You could get around this by setting up your automation to trigger when the lookup field that should have the email address isn't empty though?

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re: Also, if I set up this automation for a table that already contains records, will Airtable send emails for all existing records, or just ones I enter after turning the automation on?

Just the ones you enter after turning the automation on!

Just want to add - if you want automation to run at the right moment, and also run it for several records already in the table, add checkbox field like 'Send mail' and trigger automation to it ("When record matches condition").
Note you can bulk-check field by pasting '1' or enabled checkbox cell

Great, thank you so much!

Thank you!