Break apart email attachment if zip is too big to email

So I can send up to 25MB in an email attachment. I am looking for away to check how big the file size is and if its too big break it apart and send in two emails. (Or if there is a better way to do it)?

Here is where I am sending the email with the attachment:

public static void SendEmail(List<string> recipients, MemoryStream output, string from, string subject, string htmlMessage, bool isHtml = true)
    {
        var host = ConfigurationManager.AppSettings["emailHost"];
        var emailFrom = ConfigurationManager.AppSettings["FromEmail"];
        try
        {
            MailMessage mail = new MailMessage();
            mail.From = new MailAddress(from);
            
            foreach (var r in recipients)
            {
                mail.To.Add(r);
            }
            
            mail.Subject = subject;
            mail.IsBodyHtml = isHtml;
            mail.Body = htmlMessage;
            //string result = System.Text.Encoding.UTF8.GetString(output.ToArray());

            SmtpClient SmtpServer = new SmtpClient(host);
            SmtpServer.Port = 25;
            

            Attachment myZip = new Attachment(output, "ClientStatements.zip");
            mail.Attachments.Add(myZip);
            SmtpServer.Send(mail);
        }
        catch (Exception ex)
        {
           FMBUtilities.Logger.LogErrorToSql2012PrdAndEmailTeam("DBQueries", "SendEmail", ex);
        }
    }

Here is where i am creating the zip file to send:

if (emails.ToString() != "")
                {
                    var allEmails = emails[0].Split(',');

                    foreach (var email in allEmails)
                    {

                        if (emailValid.IsMatch(email))
                        {
                            everyEmail.Add(email);
                        }
                        else
                        {
                            return Json(new { success = false, message = $"* Not valid email address: {email}.nn * Please double check and try again." });
                        }
                    }
                        MemoryStream output = new MemoryStream();

                        List<string> distinctFiles = allPaths
                            .GroupBy(x => x.Split(new char[] { '\' }).Last())
                            .Select(x => x.First())
                            .ToList();
                        using (ZipFile zip = new ZipFile())
                        {
                              
                            zip.AddFiles(distinctFiles, @"");
                            
                            zip.Save(output);
                            output.Position = 0;
                            
                            DBQueries.SendEmail(everyEmail, output, fromAddress, "Client Statement Reports", "Here are your requested Client Statements", true);

                        }

I have found some things about setting the file size in the web.config file and things of that sort but just dont know the best way to go about this.