MailApp and GmailApp are different Apps Script services. Choose according to the operations your script actually needs, then review the resulting authorization. A script that only sends a notification does not automatically need to read the recipient’s or sender’s mailbox.
Choose MailApp for sending-only work
MailApp’s purpose is sending email; Google’s reference says it cannot access a user’s Gmail inbox. It supports message content and options such as copy recipients and attachments, subject to documented limits and account conditions.
It also exposes remaining daily email-recipient capacity. That capacity is not a guarantee of delivery, and it does not make a send idempotent. The application still needs to handle failures and uncertain outcomes deliberately.
Choose GmailApp when the mailbox operation is necessary
GmailApp supports Gmail-specific actions such as accessing conversations, labels, drafts, and messages. Review the methods you use and the authorization shown to the user. Google’s MailApp reference notes that GmailApp changes are more likely to trigger reauthorization.
Do not select GmailApp solely because it is familiar if the script’s sole requirement is a simple outbound notification. Conversely, MailApp cannot substitute for a required mailbox search or label operation.
Verify identity and behavior after a change
Test the selected service using the same execution type the production workflow will use. Check the sender, recipient, reply-to behavior, attachment scope, and quota. An installable trigger can run under its creator’s account, which may differ from the person editing the source file.
If you replace one service with the other, inspect the entire script and manifest rather than assuming old permissions disappear immediately. Review authorization through the supported process. Keep credentials and message contents out of diagnostic logs, and verify the actual sent result before allowing a larger automated batch.
Browse Gmail & Google Account help
References
- Class GmailApp | Apps Script | Google for Developers
- Class MailApp | Apps Script | Google for Developers
- Authorization for Google Services | Apps Script | Google for Developers
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.