WRONG_VERSION_NUMBER: SSL wrong version number

AnySMTPIMAPPOP

The error usually looks like this:

ssl.SSLError: [SSL: WRONG_VERSION_NUMBER] wrong version number

What it means

Your app tried to start an encrypted (SSL/TLS) connection, but the server was expecting a plain connection that is upgraded later with STARTTLS – or the other way round.

Common causes

  • Using SSL/TLS on a STARTTLS port – for example, implicit TLS on port 587 or 143.
  • In code: using SMTP_SSL with port 587 (use SMTP and starttls()), or SMTP with port 465 (use SMTP_SSL).

How to fix it

  1. Match the encryption method to the port: SSL/TLS for 465, 993 and 995; STARTTLS for 587, 143 and 110.
  2. Check the server with our email server checker to see which method each port uses.

Tools to help diagnose it

Email server checker

Check any IMAP, POP or SMTP server’s encryption, certificate and supported sign-in methods

Email server settings finder

Find the IMAP, POP, and SMTP server names, ports and encryption settings for any email address

A free tool provided by Auth-Email

Auth-Email makes your Gmail, Outlook, or other OAuth 2.0 email account available to any IMAP, POP3, or SMTP email client — no app passwords or special configuration needed.

Read the docsTry Auth-Email →

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