Several thousand people received the e-mail in April in which they were welcomed by the School of Education and Social Work, but hours later were informed in another e-mail of the apparent error.
Many receiving the e-mails had not applied to the school, and some were current and former students of the university.
The University of Sussex emphasised that the e-mail did not contain information pertaining to an offer of a place and that most would realise the information was incorrect and unintended for them.
The university further commented: “The error arose while new enquiries systems were being tested. We acted immediately to recall the email and to correct any misunderstanding that had occurred.
“People then opening their emails on Friday morning would have seen the recall email in their inboxes first, which made clear the original email was a mistake and was in any case not an official offer of a place.
“Our offers are made to candidates in the normal way through UCAS for undergraduate applicants, and by a formal letter from our admissions team for postgraduates.
“Of those who replied to us, most did so with good humour and understanding, since it was so clearly a mistake coming to them from one particular school of studies unconnected with their own subject of study.”
The Argus reported on 20 April that one unhappy applicant received the e-mail and informed her family of the news. The unnamed prospective student also informed her employers that she would be leaving her job.