Annoyingly, we ran into a problem the other day when all of a sudden our outgoing e-mail stream started to skip send-outs. On closer inspection of the e-mail account, hosted by GoDaddy, we found that the account now comes with what is termed a relay limit of 250.
So what is a relay limit?
Well basically GoDaddy refers to recipients of a mail as a relay, meaning that your relay limit is the number of recipients that can receive a mail from your e-mail account. This relay limit includes addresses specified in CC or BCC fields, so you can’t trick the system by doing something like stuffing one of those fields with a whole lot of extra e-mail addresses.
The counter is reset after every 24 hour period, and should you exceed the 250 mark for the day, the SMTP connection will fail the authentication step during the send process – which was exactly what was happening in our system before we became aware of the issue.
Exceed your limit enough times to get noticed, and you run the risk of being banned off the server completely!
Anyway, most big providers implement this sort of a send limit, 1) so that they can better fight against their systems being used for spam (which costs them money in terms of over utilized resources) and 2) so that they can up-sell increased relay limits to those willing to pay.
And now you know.