When approving emails, the system shows the following error: "Note: detected the following lines in text version that are longer than 1000 characters: Line 6 and they are not fixed. The email is now approved".
This error is an indicator that there is a large line of text in the text-only version of the email that is over 1000 characters. This occurs when there are long links in the email which will not publish correctly in the text version of it. But still the email will be approved and can be sent.
Check for excessively long links in the text version of the email and simplify them if possible.
You can test it by sending a text version of the email to yourself, or by checking the Text Only version in the Email Editor.