Azure Communication Services
An Azure communication platform for deploying applications across devices and platforms.
how to fix smtplib.SMTPAuthenticationError: (535, b'5.7.3 Authentication unsuccessful)
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(131.20000000000002, 64%, 22%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ENG%3C/text%3E%3C/svg%3E)
Nayan Gajjar
0
Reputation points
getting smtplib.SMTPAuthenticationError: (535, b'5.7.3 Authentication unsuccessful)
on email auth it was working till yesterday, suddenly stopped how to fix it?
Azure Communication Services
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(153.6, 51%, 24%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EAN%3C/text%3E%3C/svg%3E)
Aditya N 3,890 Reputation points Microsoft External Staff Moderator2026-04-13T06:53:20.7366667+00:00 Hello @Nayan Gajjar
Thank you for reaching out Microsoft Q&A. Please could you elaborate your issue from which module in Azure you're getting this error.
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Aditya N 3,890 Reputation points Microsoft External Staff Moderator
2026-04-14T10:31:10.21+00:00 Hello @Nayan Gajjar
Following up - please could you let us know from where exactly this error is getting populated.
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