SMTP Restrictions
Our upstream providers have placed restrictions on their SMTP servers in order to prevent abuse. These limits are as follows:
Limitations in place on smtp-is.zsd.co.za and smtp-za.zsd.co.za
Policy:
- The end user can only send to a maximum of 100 recipients per mail message, this includes To:, Cc: and Bcc:.
- The size limitation is 102.4 Mega Bytes per message.
- Relaying is only allowed from IS DSL ip ranges.
- The sender and recipient domains must be a Fully Qualified Domain Name and be a valid resolvable DNS domain.
- No sender From: addresses from free mail services, i.e. Yahoo, Hotmail, GMail, etc are accepted.
- Testing for open relays on the IS DSL user ip space and blocking access to these abusers.
- Blacklisting and block ip's identifying themselves as one of the smtp servers.
- Blacklist ip's sending mail to known spam traps for a minimum of 1 hour.
- Manual process of blacklisting domains and/or sender addresses due to abuse complaints being logged.
- Rate limiting incoming mail from client connections to 50 recipients max per minute.
- Rate limiting incoming connections from client connections to 7 per unique ip on each server.
- Reject any mail that has more than 50 MIME parts.
- Reject any mail considered to be malware infected.
- Reject any mail looking like spam.
Technicial Policy:
- Max recipients in a single connection - 100
- Max mail size including the encoding of the mail - 100MB
7 Concurrent connections per server. Total concurrent connections -> 28
Limitations in place on smtp-sx.zsd.co.za
- 25 recipients per message
- 250 MB traffic per hour
- 300 recipients per hour
- 1000 recipients per 24 hours
- Users are not allowed to send to 3 or more AOL, Yahoo or Hotmail email accounts in the same email.