What are the limits for MX Outbound (SMTP Mail Relay)?


All MXTools servers (MX Outbound, SMTP SmartHost and Mail Relay) have the following restrictions and limits:

  • Maximum number of recipients is 200 per email. This exceeds the RFC2821 which defines the email protocol which recommends 100, and is best practice. Although MXTools supports 200 recipients per email it is best practice to fine tune your email software to 100 or less as not all email clients conform fully to the RFCs
  • Maximum of 50 concurrent connections
  • Maximum of 120 connections per minute.

These figures are needed for you email marketing software when setting rate limits for the outbound SMTP Server.