Unprecedented usage and a high volume of cyber-attacks have strained Yale’s e-mail system during the last two weeks, causing glitches and slowed performance throughout the University.

On Thursday, Yale officials announced that the disk space used by e-mail grew 39 percent last semester, pushing the central campus servers to their limits. A series of worm and virus attacks exacerbated the problem, forcing the University to order new servers to field the increased traffic. Officials said they are also urging users to decrease the size and volume of e-mails stored on their inboxes, but some students said they are unlikely to change their e-mailing habits.

Chief Information Officer Philip Long said the space devoted to e-mail has already exceeded its expected growth for the school year.

“We used up our entire year’s growth last semester,” he said. “What happens with e-mail is it degrades slowly for a while, and when it gets bad, it gets awful.”

When worms and viruses started to flood inboxes two weeks ago, students experienced login problems, slow performance, and delayed message deliveries, officials said. The University has ordered two new servers to eventually increase capacity by 33 percent, some of which should be available by mid-February. Though the price of the new servers is on the scale of $100,000, Long said the purchases will not seriously impact the department’s budget because he had been planning to purchase them at the end of the school year.

Information Technology Services officials are encouraging students to move old inbox messages to other folders, specifically contacting the 500 students with the largest inboxes on campus. Students who store messages with large attachments have been a main source of strain, Long said.

“E-mail is a very convenient way to send stuff around, but e-mail was never intended as a file storage system, and that tends to clog performance,” Long said.

But some students reacted skeptically to ITS’ request, saying that slower performance is a small price to pay for keeping themselves organized.

“You never know when you need your e-mails again, so I just don’t delete,” Debbie Li ’08 said. “When I tried to move everything to different folders, I was putting the wrong e-mails in the wrong folders, and I couldn’t find anything.”

Several other students said they had tried to use the system’s monthly preventative maintenance program, but it had no effect on their inboxes.

ITS officials are also asking students with e-mail supplements like Outlook to adjust their settings to ease the strain on Yale servers. For example, while Outlook often accesses the servers to check e-mail once every 10 seconds, users can change the program settings to check for new messages once every 10 minutes.

The immediate cause of the slowdown was a worm attack the week of Jan. 16 and a message containing a virus that reached 4,000 students before ITS blocked it, Information Security Officer Morrow Long said. The virus message asks students to download its contents in order to see footage of a rape. Officials said they are not especially concerned about widespread infection, given that the University changes the attachments’ file extensions to make it harder to download them accidentally, but the volume of e-mail generated by the attacks triggered a slowdown.

“The worms have been a source of extra traffic, slowness, and also the possibility of some infections,” Morrow Long said. “We see a lot of spam normally, but we’ve seen a lot more e-mail carrying malicious payload.”

ITS plans to relieve the burden on the servers by improving its filtering programs. Officials are on the lookout for another worm programmed to damage infected computers this Friday, but no infections have been detected on Yale computers so far.