Possible null reference argument for parameter 'host' in 'Task MailService.ConnectAsync(string host, int port, bool useSsl, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference argument for parameter 'host' in 'Task SmtpClient.ConnectAsync(string host, int port = 0, SecureSocketOptions options = SecureSocketOptions.Auto, CancellationToken cancellationToken = default(CancellationToken))'.

Possible null reference return.

Converting null literal or possible null value to non-nullable type.

Possible null reference return.

Non-nullable property 'Subject' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'PerformedBy' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'Message' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Nullability of type of parameter 'value' doesn't match overridden member (possibly because of nullability attributes).