ParameterAlwaysQuote Property

public bool AlwaysQuote { get; set; }

Property Value

Gets or sets whether the parameter value should always be quoted even if it normally wouldn't need to be.

Technically, Content-Type and Content-Disposition parameter values only require quoting when they contain characters that have special meaning to a MIME parser. However, for compatibility with email processing solutions that do not properly adhere to the MIME specifications, this property can be used to force MimeKit to quote parameter values that would normally not require quoting.

Reference