Error
"Plaintext authentication disallowed on non-secure (SSL/TLS) connections"
Resolution
Fix this issue by changing the settings on your IMAP server to allow plaintext over SSL/TLS.
Certain IMAP Source servers disallow plaintext authentication on non-secure SSL/TLS connections. If this is the case, migrations will report an error similar to the following:
Source: "Your migration failed checking Source credentials. [PRIVACYREQUIRED] Plaintext authentication disallowed on non-secure (SSL/TLS) connections."
The exact location of this setting differs between IMAP providers, but it can normally be located under Security Settings.