Dame Priti Patel visited the Royal Mail delivery office in Moorside, Colchester, around 11am, after receiving complaints from residents.
She met with Royal Mail director of public policy David Gold, and members of the Colchester branch leadership team to discuss ongoing issues with deliveries to some postcodes in the area.
The main areas impacted in her constituency have been Coggeshall and Layer De La Haye.
Dame Priti said she had been contacted “by a number of constituents” who have been affected by delays of post being delivered to their homes, and the delays have caused “serious concern”.
Postal delays have led to residents missing hospital appointments, and the MP raised concerns with the Royal Mail team in a bid to ensure post does arrive without delay in future.
Dame Priti said: “I would like to thank Royal Mail for meeting with me and listening to the serious cases I have raised with them on behalf of my constituents.
“It is very concerning for residents when their post does not turn up on time, particularly when it relates to someone’s health and doctor or hospital appointments.
“I have pressed Royal Mail on their plans to turn things around and ensure these issues impacting delivery of mail six days per week are resolved.
“I have been assured that they are doing everything to make sure that residents receive their post on time, and I will continue to work with the residents impacted and hold Royal Mail to account on their performance.”
A Royal Mail spokesman said: “We were happy to host Dame Priti at our Colchester delivery office to reassure her that we are doing everything we can to ensure that residents receive their post on time.
“Improving the reliability of our service is one of our top priorities, and we are working hard to deliver the standard of service our customers in Colchester expect.
“We will remain in contact with Dame Priti about this going forward.
“We’re also very grateful that she has committed to helping us raise awareness locally of career opportunities at Royal Mail as we seek to recruit new staff at Colchester.”