Email delays are not uncommon, especially on large ISP networks like Earthlink, Verizon, AT&T, and Time Warner. Email does not always move as fast we would want them to, as there are sometimes many moving parts (and potential points of failure) between the point of origin of a message and its final intended destination.

Mail can move through many intermediate servers, routers, firewalls, intrusion detection devices, spam filters, and virus scanners (on both ends of the connection) long before it reaches its final point of delivery.

Sometimes, an email queue on one end or the other of a connection might get backed up and must process some of the backlog before it will accept more mail. Other times, email traffic volume will max out the number of connections that a server is configured to handle at one time and another sender must complete their transmission and release the connection before another server can connect.

These are usually temporary issues and resolve themselves in a matter of minutes or hours. In rare cases delays can last up to several days.

Current internet email standards state that a mail exchanger should continue to attempt delivery for 72 hours, if delays are encountered, before bouncing the message back to the sender.

Here at ICOMEX, our mail severs are currently configured to accept up to 64 simultaneous connections for inbound email. With the exception of when we had the DDOS against another client, we generally don't get more than 2 - 4 concurrent inbound connections at any given time, with a peak of generally less than 12. Inbound and Outbound email processing queues are typically less than 2 seconds.