On this page, you will find more information about the most common causes and most relevant solutions for the Yahoo! Mail error '421 4.7.1 [TS03]'. Do you need help straight away? Visit our support page.
The Yahoo! documentation indicates that error code '421 4.7.1 [TS03]' is caused by the following problem: "Yahoo Mail is getting a high volume of emails from your server which is indicative of “Spam” or “unsolicited emails”.".
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