C# Collect all Errors and send one Email when Programm is finished using log4net

Is there a way to collect all exceptions with the level value Error and combine them into one E-Mail? Currently I will get one E-Mail for each Log.Error(ex) in my programm.

Edit: I know that the bufferSize with value one, will cause to send the mail if Log.Error is called. But raising it up, causes send all logging events(info...) in the same mails as the Error.

My Log4Net Config:

<appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">
    <to value="xxx@xxx.email" />
    <from value="xxx@xxx.email" />
    <subject value="oops there is an error" />
    <smtpHost value="host@host.host" />
    <port value="25" />
    <bufferSize value="1" />
    <lossy value="true" />
    <evaluator type="log4net.Core.LevelEvaluator">
        <threshold value="ERROR" />
    </evaluator>
    <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%newline%newline%newline%date [%thread] %-5level %logger [%property{NDC}] - %message%newline%newline%newline" />
    </layout>
</appender>