In the world of multichannel marketing, it’s critical to have accurate information related to offline customer touchpoints.

Daunting as this information might be, competent mail service providers today have the experience, data and tools to help mailers build accurate and predictable mail distribution plans. The best can also help deal with or overcome breakdowns in USPS delivery performance.

Understanding USPS Delivery Performance

The USPS has Service Standards, giving it complete latitude as to how much or how little mail is in-home prior to the last day of the Service Standard. But how much mail are they able to process and deliver in one day, two days, three days and beyond?

The Postal Service generally moves mail First In, First Out, as quickly as possible. Its freedom in the amount of mail delivered prior to the last day of the Service Standard means that mailers need to keep tabs on how the USPS is doing.

Standards vary by mail class

Many ask, “What time does the USPS deliver?” The answer varies based on mail class. The Service Standard for First Class mail is perhaps the easiest to understand.

The Critical Entry Time (CET) is the cutoff time for mail to be processed the same day it is dropped at the postal facility. It is expressed in 24-hour increments. For First Class Mail the CET is 8:00 AM. Mail destined for ZIP codes within the SCF area that it is entered into should be in-home next day. Mail destined for ZIPs within 300 miles of the entry point is to be in-home on Day 2. All other mail for the continental U.S. should be in-home by Day 3. Alaska and Hawaii mail should be in-home by Day 5.

The Service Standards for Standard Mail are also fairly straightforward when calculating USPS delivery times. If mail is delivered to a National Distribution Center (NDC) prior to 16:00, the Service Standard is 1-5 days from that date. SCF Mail delivered prior to 16:00 on a Friday or Saturday has a Service Standard of 1-4 days. And SCF mail delivered prior to 16:00 any other day of the week has a Service Standard of 1-3 days. If mail is delivered after 16:00, it is considered delivered the following day and does not make the cut off for processing that night. So 16:00 is the Critical Entry Time for Standard Mail.

Processing complicates things

On the surface, Service Standards for Periodical Mail are fairly straightforward. Mail delivered to an SCF facility and addressed within that SCF area is to be in-home the next day. Mail delivered to an Auxiliary Distribution Center (ADC) or NDC, containing only mail for that area has a Service Standard of 1-2 days. But the CETs vary based on whether the periodicals can be processed by machine. This makes determining the dates the mail will be in-home more challenging.

The automated equipment for processing magazines, which the USPS calls flats, is called the Flats Sequencing System (FSS). It sorts flats into the order that Postal Carriers walk their routes. This sort eliminates the need for Carriers to ‘case’ their mail prior to going out on routes. This saves time on the Carrier side — theoretically allowing them more time to deliver more mail.

Only certain zip codes run on FSS machines. They cannot handle all mail in a facility, and many facilities do not even have one. Currently only about 80 of the original 100 machines are actively being used.

Additionally, pallets of machinable flats destined for the FSS must meet critical pre-sort levels upon entering the postal facility. An FSS scheme pallet is a pallet of mail for one specific ‘scheme’, ZIP or set of ZIPs that the machine will process in one run.

If the mail is for an FSS ZIP and on an FSS scheme pallet, requiring no bundle sorting, the CET is 11:00. If mail is for an FSS ZIP and on any other type of pallet, the CET is 08:00. The CET is 16:00 for non-FSS mail on a 5-digit level pallet and 17:00 for non-FSS mail on any other type of pallet.

The bottom line is that Periodical Mail has a 1-2 day Service Standard, but only for certain qualifying pallets delivered by a certain time. Often it’s actually three days before mail is in-home after delivery to an ADC or NDC, and two days after delivery to an SCF.

Dealing with variability

Intelligent Mail barcode (IMb) scan data is the key to knowing how mail is performing in the USPS system. This data provides both an overall view and performance by each USPS facility. If timing is critical, the variability in Service Standards can be problematic. And USPS performance is heavily influenced by volume fluctuations over the year.

Mailers can expect a much higher percentage of June mail to be in-home just one day after delivery to an SCF than in November, when volume is much higher. More mail will shift to the window’s tail end or later in the heavy-volume months of September-December.

But no matter the month, it’s common for delivery to push beyond the Service Standard window. Keep in mind that some facilities won’t be able to deliver any mail during the Service Standard window during the busiest weeks.

The Service Standard is not a guarantee for in-home dates — the USPS won’t refund costs for First Class, Marketing Mail or Periodicals that it delivers later than expected. Referencing past years’ data helps to determine what may occur the same week or month in the current year. But there are always variances.

Below is a general outline of how the USPS performs throughout a typical year, and reflects general USPS delivery times:


The year starts with a second wave of package volume in gift returns. Performance recovery from the holidays usually begins by week two. However, the MLK holiday prevents a full recovery to normal service performance.


Typically consistent delivery performance with some fluctuation.


The best delivery months of the year, as volume is very low.


Expect some mid-month slowing as back-to-school catalogs cause some disruption.


First fall catalogs mail and cause a slight dip in performance, usually the first and third weeks of the month.


The week of Labor Day is usually a “good” delivery week, as the USPS prepares for it. The week following the holiday is the first slower week of the fall season. The last two weeks of the month usually are back to near-August levels.


Performance typically drops mid-month as Christmas catalogs mail heavily at this point. Political and election mail volume in election years can impact service as additional volume and focus on moving ballots slow overall delivery performance. The last week of the month is usually one of the three slowest delivery weeks of the year due to the heavy volume.


Delivery from mid-October through the first week of December remains slow, but the slowest week is right after Thanksgiving when volume is extremely high as most catalogers mail their last big holiday push that week and package volumes peak from Black Friday events.


After the first week of the month, Standard mail delivery times may increase slightly because quantity drops precipitously, but this mail volume is still competing with peak holiday package volume. The USPS prepares for the First Class and Parcel surge, and facilities that do not get overwhelmed will typically move the mail very quickly. Specific processing plants that get overwhelmed will likely completely miss the service standard. The two days prior to Christmas typically slow down, as USPS focus shifts to that First Class mail. The period between Christmas and New Year’s is difficult – there are two days with no processing and in some years it’s even more depending on when Sundays fall. Distribution companies lose days they can ship and deliver to the USPS.