Residents who have waited days for "urgent" deliveries say they have been "left in the dark" by the Royal Mail.
Tony Robson, who lives in Bristol Gardens, Kemp Town, has waited more than a week for post including a tax rebate cheque which he needs to tide him over until his pension payments begin.
The 66-year-old is also waiting on at least three parcels.
Mr Robson contacted the Royal Mail via X, formerly known as Twitter, and did not receive a reply for several days.
He said when he asked at the local post office, they were unable to answer his queries.
"I just think it is unacceptable to be completely left in the dark. People rely on the postal service for all sorts of things, including doctor's letters," said Mr Robson.
When Mr Robson eventually received a reply from the Royal Mail on X, he was told the office has been reporting issues with high staff absence levels that will be affecting deliveries.
"The complaint will be resolved internally, and therefore you won’t receive an update however I expect you to see an improvement in service soon," said the spokeswoman in a message on X.
"Once again I apologise for the issue, and thank you for bringing this matter to our attention."
Tony said he would not mind so much about the delays if he and other Kemp Town residents were being kept informed.
A spokeman for Royal Mail told The Argus: “We are sorry to residents who have experienced delays. There has been some slight disruption to service at the local delivery office, in part caused by vacancies and sick absence. We are actively recruiting to fill the delivery office and have plans in place to ensure mail is being delivered on a reliable basis. We expect residents will begin to see a return to regular service.”