ASPnix implements email limitations on its shared services to ensure the stability and performance of the mail systems while preventing abuse, spamming, and over-usage. These limits apply to Windows SmarterMail environments on shared hosting, VPS, and dedicated servers that use the shared mail servers. The enforced restrictions are: 5000 outgoing emails per 24-hour period per user, 50MB maximum message size (including attachments and MIME encoding), 100 recipients per message, 25 bounced emails per 24-hour period per user, and 1000 connections per hour per IP address.

If sending to 100 or more recipients, the mailing list feature must be used. Subscribers generating 3 or more bounces must be removed to avoid complaints. Reaching connection or other limits results in the offending IP being blocked for 1 hour. ASPnix reserves the right to remove high-bounce subscribers without notice. These rules protect shared infrastructure and maintain deliverability for all customers.

#Why These Email Limits Are Enforced

Shared mail servers process traffic from many accounts at once. Without controls, a single user or compromised script could overload CPU, memory, disk I/O, and bandwidth, degrading service for everyone. High-volume sending also risks damaging the server's IP reputation with major receivers. Once an IP lands on blocklists, legitimate mail from all customers suffers. The 5000-email daily cap supports typical transactional and notification use while blocking mass unsolicited mail. The 50MB message limit prevents oversized attachments from consuming excessive resources. Connection throttling stops rapid-fire scripts from saturating SMTP listeners.

#Detailed Breakdown of Limits

All limits are strictly enforced on outgoing mail. Monitor usage through SmarterMail statistics to stay compliant. The core restrictions are:

  • 5000 outgoing emails per 24-hour period per user
  • 50MB max message size (including message, attachment(s) and MIME encoding)
  • 100 recipients per message
  • 25 bounced emails per 24-hour period per user
  • 1000 connections per hour for all services (per IP address)

For newsletters, marketing emails, or any communication targeting 100 or more recipients, use the mailing list feature inside SmarterMail. Sending large recipient lists in individual messages violates the per-message cap and is inefficient.

#Bounce Management and List Hygiene

List subscribers that have 3 or more bounces will need to be removed from the list to prevent abuse complaints. Poor list quality quickly triggers ISP feedback loops and increases the chance of blacklisting. Regularly purge invalid addresses, honor unsubscribe requests, and avoid purchased or scraped lists. ASPnix reserves the right to remove subscribers with 3 or more bounces at any time without notice to protect the shared mail platform.

#Consequences of Exceeding Limits

If the connection limit is reached or exceeded, the offending IP address(es) will be blocked for 1 hour. During this block, no SMTP, IMAP, or POP3 connections are permitted from that IP. Repeated violations can lead to longer reviews or stricter account-level controls. Applications that send mail must incorporate throttling, batching with delays, and error handling for temporary blocks.

#Best Practices for .NET Applications

When sending mail from ASP.NET or other .NET code, the same server-side limits apply. Instantiate SmtpClient once, reuse it where possible, and avoid opening new connections for every message in a loop. Track daily volume in your application database if sending high volumes. Implement exponential back-off on transient errors. Always set realistic From addresses and handle bounce notifications via SmarterMail's feedback mechanisms.

csharp 
using System.Net.Mail;
using System.Net;

public void SendMail(string recipient, string subject, string body)
{
    using var smtpClient = new SmtpClient("mail.yourdomain.com", 25);
    smtpClient.Credentials = new NetworkCredential("user@yourdomain.com", "password");
    smtpClient.EnableSsl = false;

    using var message = new MailMessage("from@yourdomain.com", recipient, subject, body);
    smtpClient.Send(message);
}

// Note: Add logic to enforce your own daily limits below 5000 emails and space out sends to avoid hitting the 1000 connections/hour cap.

Stay well below the published thresholds with a safety margin, maintain clean subscriber lists, and use SmarterMail's list tools for bulk mailings. Regular review of bounce reports and sent-volume statistics will keep your domain in good standing and prevent unexpected blocks.