Visitors to AT&T’s (T) website trying to pre-order an iPhone 4 Wednesday morning got the message posted at right: “Pre-orders for iPhone temporarily suspended.”

Behind the scenes, AT&T employees were alerted of the suspension by an internal memo that tells us more than we need to know about AT&T’s operations, including the names of its servers. Here, via TheBoyGeniusReport, is the text of that memo:

Pre-orders for iPhone 4 and iPhone 3GS 8GB are Temporarily Suspended

Effective close of business on June 15, 2010, the ability to place pre-orders (new activations, upgrades and exchanges) has been temporarily suspended.  There is a special team that will be manually working all pre-orders from June 15th that were held in a pending status.  Under no circumstances should new pre-orders be attempted in the system.

This suspension impacts Phoenix, Premier, OPUS (COR), and System X (DMDR).

Please stay tuned to future bulletin communications for any updates.

Despite the snafu, Apple (AAPL) is expected to sell record numbers of iPhones when the new model goes on sale Thursday, June 24.

See also:

• How many iPhones did Apple just sell?
• Apple Store app crashes on launch
• iPhone 4 (not) available for pre-order
• Japan avoids an iPhone 4 meltdown

[Follow Philip Elmer-DeWitt on Twitter @philiped]