Inbound SMTP Restrictions
In order to provide the highest level of service our inbound injection network has the restrictions listed below when injecting inbound messages for relay.
-Maximum of 20 simultaneous connections per IP may be established to smtp.socketlabs.com
-Maximum message size, including any embedded images and attachments, is 40MB
-Maximum 500 total recipients per message
See our other KB articles for more information on related topics.
IP Addresses, Ports, and more inbound SMTP connection information: http://support.socketlabs.com/kb/94/
To better troubleshoot and diagnose SMTP connectivity issues see our blog on Diagnosing SMTP Service Connection Issues
If your message is larger than 40MB you will receive the following error: 552 5.3.4 - Message too big for system
For more information about this error please see http://support.socketlabs.com/kb/87/
If you attempt to send to more than 500 addresses in one message you will receive the following error: 452 5.5.3 - Too many recipients
For more information about this error please see http://support.socketlabs.com/kb/85/
If you attempt more than 20 connections you will receive the following error: 421 4.4.5 - Too many connections from your host
For more information about this error please see http://support.socketlabs.com/kb/86/