Kenneth D. Smith (Smith) appeals from a decision of the Merit Systems Protection Board (board), 26 M.S.P.R. 185, sustaining his removal from United States Postal Service (Postal Service) for assaulting a police officer. We affirm.
Background
(1) The Removal
In March 1982, the Postal Service sought to remove Smith for “engaging in a physical altercation with another postal employee.” Smith filed a grievance and was represented at a Step 1 hearing by a union Shop Steward, J. Applewhite, who made oral reply on Smith’s behalf. Smith was reinstated, but “on a last chance basis.”
At 3:17 a.m. of March 10, 1984, Smith was seen carrying a fur coat from the J.A. Farley Building at which he worked. Smith became involved in an incident with Postal Police Officer Vincent Condon and Postal Police Sergeant Michael Padro. He was restrained and then transported to Morgan Headquarters, where he refused to surrender his photo identification. At that time, Officer Condon placed Smith under arrest and he was taken to Central Booking, where he was charged with the crime of resisting arrest.1
On March 20, 1984, the Postal Service sent Smith four copies of a Notice of Proposed Removal (Notice): by certified and regular mail to 2140 University Ave., Apt. 2B, Bronx, New York 10468; and by certified and regular mail to 1504 Sheridan Ave., Bronx, New York 10457.
On that same day, the Postal Service mailed a copy of the Notice to Smith’s union representative, who arranged for a grievance proceeding Step 1 hearing on April 3, 1984.
The Notice set forth charges of assaulting a Postal Police officer, engaging in disorderly conduct, and resisting arrest, and cited the 1982 disciplinary proceeding.
The notice provided that:
You may answer this notice personally or in writing, or both to the undersigned [i.e., Daniels] or the Postmaster’s Desig-nee in my absence at the JAF Building, Outgoing Mails Section, Tour 3, New York, New York 10199, and may submit affidavits in support of your answer____ You will be allowed seven (7) calendar days from the date you receive this notice to submit your answer. Full consideration will be given to any answer you submit. As soon as possible after your answers) is received, or after the expiration of the seven (7) day limit, if you do not answer, you will be given a written decision.”
The Notice also provided that “you have the right to file a grievance under the Grievance-Arbitration procedures set forth in Article 15, Section 2 of the National Agreement within 14 days of your receipt of this notice.”
*1542When Smith did not appear at the April 3 Step 1 hearing, oral reply was made on his behalf by Shop Steward J. Applewhite. Smith says he did not receive the Postal Service’s Notice until April 5, 1984.2 He also says that on April 18 he attempted to contact Supervisor Daniels to obtain a Step 1 hearing, but was “denied access to the building.”
The Postal Service’s Letter of Decision was dated April 5, 1984. In it, the deciding official, Tour Superintendent Robert Pellot, stated that he had given “full consideration to the oral reply” made on Smith’s behalf by Shop Steward Applewhite, and that removal was appropriate in view of Smith’s past disciplinary record and the seriousness of the charge. The removal was to become effective April 23, 1984.
(2) The Hearing Before the Presiding Official
Officer Condon testified that: Smith approached him carrying a brown bag containing a fur coat, but could not produce a receipt or -property pass; Smith at first refused to return to the facility to obtain a property pass, but later went inside; Officer Condon’s supervisor, Padro, arrived at the scene; Smith returned with his package and ran through the doors; Officers Con-don and Padro chased and apprehended Smith, who swung at Officer Condon and pushed him up against the wall; Smith was arrested for resisting arrest. Condon’s testimony was corroborated by that of Officer Padro.
Smith testified that: he received the fur coat from a co-worker to show it to his wife; Officer Condon stopped him at the facility exit and demanded that he show his property pass; he returned inside to obtain a pass, but was unsuccessful; he returned to the exit and heard the guard yell “incoming” and the elevator door slam; both noises reminded him of his Vietnam experiences, and his automatic response was to take cover; he ran outside and got between a van and car; Officer Condon came up and accused him of stealing the coat; he never assaulted either officer.
Arthur Head, an agency employee, testified for Smith that: he saw Smith talking with the two officers; he saw no violence; when asked if there was a problem, Smith said everything was “all right”. Smith also introduced an affidavit of Vaughn, an agency employee, who stated that “from what he was able to see” Smith did not swing at the officers.
Tour Superintendent Pellot testified that he considered an assault on a Postal Police Officer to be a serious charge warranting removal. Supervisor Willie Daniels said that, in proposing removal, he based his decision on the officers’ written reports, and that his concern was not for the ownership of the fur coat, but, noting Smith’s past disciplinary record, for the safety of the facility.
(3) The Presiding Official’s Opinion
The Presiding Official credited the testimony of Officers Condon and Padro, saying their statements “were candid, complete and plausible.” The Presiding Official noted that neither Head nor Vaughn testified that he had seen the entire incident, and that the statements of neither contradicted those of the two officers. The Presiding Official found Smith’s version of the incident “totally implausible”.
The Presiding Official held that the Postal Service had carried its burden with respect to the charge of assaulting a Postal Police Officer. She further concluded that nexus to the efficiency of the service was *1543clear, and that the agency had not abused its discretion in determining the appropriate penalty.
In respect of Smith’s affirmative defenses, the Presiding Official determined that Smith had not shown error in the agency’s holding a grievance with only the union representative present. Assuming, ar-guendo, however, that such were error, she further held that Smith had not established that it was harmful, reasoning that “[t]he Board’s hearing is de novo, thus any prejudice to the appellant could have been cured before the Board.”
(4) The Decision of the Full Board
The Full Board denied review. It commented, based on Smith’s allegation of late notice, that the Postal Service erred in failing to afford Smith the full thirty days’ notice, as required by 5 U.S.C. § 7513(b)(1). On the basis of the record before it, however, the board concluded that any error in this case did not warrant reversal because Smith had not shown “by a preponderance of the evidence that the procedure likely had a harmful effect upon the outcome before the agency.”
OPINION
Though Smith says an issue in this case is whether substantial evidence supports the board’s conclusions, he presents no argument and cites no evidence to support a reversal on that ground.3
Smith’s asserted basis for this appeal is that the agency action “should be reversed because the petitioner was denied due process,” effectively asserting per se harmful error “in that Petitioner was not given the opportunity to defend himself in the Step One hearing.” The government responds that “any error that may have occurred was clearly cured at the MSPB hearing where Smith presented his reply to the charges at a de novo proceeding.” We reject both contentions respecting harmful error as too broadly stated.
(1) Constitutional Due Process
No basis exists for Smith’s assertions respecting constitutional due process. Smith has not shown that he was denied the necessary minimum due process, “some pretermination opportunity to respond,” to which he is entitled under the Constitution. See Cleveland Board of Education v. Loudermill, — U.S.—,—, 105 S.Ct. 1487, 1493, 84 L.Ed.2d 494 (1985); see also DeSarno v. Department of Commerce, 761 F.2d 657 (Fed.Cir.1985). The record here establishes that Smith had “opportunity”. His union representative presented an oral reply on Smith’s behalf. That same procedure was used in connection with Smith’s 1982 grievance and with positive results. We have been shown no basis for assuming that the union was representing itself and not Smith in this case. That Smith’s union representative was not successful in gaining for Smith a second “last chance” does not in itself mean that that representation supplied him less than due process. Because Smith’s oral reply was fully considered by the deciding official, it must be deemed to have satisfied the due process minimum.
Were we convinced that Smith had been denied his right to constitutional due process by agency action, negligence, or design, and in the face of even a reasonable effort by Smith to assert that right, reversal would promptly follow. None of those factors is present here.
Nothing in this record indicates even remotely that the agency sought to deny Smith any of his rights, or neglected its duty, or in any manner played “fast and loose” with the procedures designed to insure protection of employee’s rights.
Assuming that Smith did not receive the Notice of Proposed Removal until April 5, *1544nothing of record indicates that he attempted to present, and there is clearly no evidence that he was prevented from presenting, oral or written reply to Daniels during the period April 5-23.
Thus Smith failed to avail himself of his statutory right to answer orally and in writing at the agency level, 5 U.S.C. § 7513(b)(2), by failing to request a hearing within seven days of receiving his notice of removal.
Nor does anything in this record suggest that Smith made any true effort whatever to obtain a Step 1 hearing at which he might be present. To the contrary, the record establishes that all he did, or said he did, was go to the JAF building, be “denied access”, and leave.4 On the present record, Smith made no phone calls, sent no letters or telegrams, and made no complaint to his union.
Though the Notice told him of his right to request a Step 1 hearing within fourteen days after April 5, there is not a word of testimony or scintilla of evidence in the record before us showing that, at any time between April 5 and April 23, Smith telephoned or wrote to Daniels’ office, or contacted his union representative, or took any other reasonable steps to request a Step 1 hearing or to otherwise exercise or protect his grievance rights. Moreover, nothing here suggests that Smith petitioned for reconsideration of the Decision Letter, or did anything else at any time that might have put the agency on notice that he was either seeking a hearing or alleging any procedural error.
The agency’s first notice of Smith’s due process allegations occurred at the time of the hearing before the presiding official. Absence of notice to the agency would be of no moment if an actual denial of constitutional due process were present. Agencies can be presumed to know the rules. Yet, in the context of the present case, where Smith remained silent until he got to the board, the absence of opportunity to rectify the error is illuminating. The agency, for example, could not have known that Smith, as he first said before the board, did not receive its Notice until sixteen days after it was mailed. If agencies could not rely on the due course of the mails, they could never safely act, for the employee could always wait till he is removed and then, before the board, claim late receipt of the Notice. During the pre-termination period, the agency could have justifiably presumed that Smith had received the Notice by March 23d or 25th, had elected not to attend the April 3 hearing, and had decided to present his oral reply through his union representative.
In all events, agencies are not psychic. The agency and Smith knew that he had been given a “last chance” in 1982, and his failure to appear personally at the April 3 hearing may have been thought to arise from a feeling of futility on his part. Absent some notice by Smith, the Postal Service could not have had, and could not have obtained, knowledge of any failure of the mails or other defect in pre-termination procedure and could have had no reason to rectify the situation by a sua sponte scheduling of a new Step 1 hearing.
The statute, 5 U.S.C. § 7513(b)(1), calls for receipt of written notice thirty days before an adverse action may be taken. Smith was removed thirty-four days after the agency had mailed its Notice to him. If Smith’s testimony that he first received any Notice on April 5 be accepted as true, as it must be on this record, we would necessarily conclude that Smith was inadvertently accorded eighteen days notice from that date of receipt of notice, i.e., twelve days less than the period prescribed. The board recognized that as agency error, though the record does not indicate how the agency could have known that Smith had not received any of its four letters to him until April 5. If error there were, as indicated below, it was not in this case harmful and does not compel reversal return to duty, and payment of back pay to *1545Smith. The agency cannot be penalized and the public fisc cannot be charged as a result of an event (late Notice receipt) so inconsequential in this case that Smith did nothing for eighteen days, except go once to the JAF building.
As the Supreme Court noted in Louder-mill, “[tjhere are, of course, some situations in which a post-deprivation hearing will satisfy due process requirements.” —U.S. at—n. 7, 105 S.Ct. at 1493 n. 7. Were it necessary to decide, the present would be one such situation. Here, it is uncontroverted that at least eighteen days before the removal took effect, Smith had written notice of the charges against him, an adequate explanation of the agency’s evidence, notice of the intent to remove him on April 23, and opportunity to request a Step 1 hearing. As above indicated, it cannot be controlling that the oral reply made by his representative was not successful at the April 3 hearing.5 Having made no reasonable effort to approach the agency for eighteen days after receipt of notice, Smith nonetheless had the opportunity to do so during that period, and thereafter made a full presentation of his case de novo before the board. See Doyle v. Veterans Administration, 667 F.2d 70, 72 (Ct.C1.1981). Under all the facts of this case, we cannot conclude that Smith was deprived of constitutional due process.
(2) Harmful Error
Though treated separately here, denial of due process and harmful error are in this case intertwined. Both rest on Smith’s late receipt of notice.
For purposes of the harmful error rule, 5 U.S.C. § 7701(c)(2)(A) (1982), “[ajn employee who elects to appeal an agency disciplinary decision to the Board must prove that any procedural errors substantially prejudiced his rights by possibly affecting the agency’s decision.” Cornelius v. Nutt, — U.S. —, —, 105 S.Ct. 2882, 2890, 86 L.Ed.2d 515 (1985); see also Mercer v. Department of Health and Human Services, 772 F.2d 856 (Fed.Cir.1985).
The board defined “harmful error” in 5 CFR § 1201.56(c)(3) as “[e]rror by the agency in the application of its procedures which, in the absence or cure of the error, might have caused the agency to reach a conclusion different than the one reached.” In Parker v. Defense Logistics Agency, 1 MSPB 489, 1 M.S.P.R. 505 (1980), the board further refined the inquiry, saying “the question is whether it was within the range of appreciable probability that the error had a harmful effect upon the outcome before the agency.” Id. at 493, 1 M.S.P.R. at 514. Though further judicial refinements may be possible, the board’s interpretation of the harmful error rule is entitled to substantial deference, and has been approved by the Supreme Court. See Nutt, — U.S. at —& n. 14, 105 S.Ct. at 2889 & n. 14.
It is Congress’ clear intent that agencies have a “greater ability to remove or discipline expeditiously employees who engage in misconduct,” S.Rep. No. 95-969, p. 51, 1978 U.S.Code Cong. & Ad.News 2723, 2773, and that unnecessary reversals of agency actions because of technical procedural oversights be avoided. Nutt, — U.S. at —& n. 17, 105 S.Ct. at 2891 & n. 17. Thus, though an agency commits a procedural error, reversal by the board is unwarranted unless that error casts sufficient doubt on the reliability of the agency’s factfinding or decision. See id. at 2891. On review of the board’s decision on the harmful error question, as on all others, our review is limited by the standard set forth in 5 U.S.C. § 7703(c).
As above indicated, we do not accept Smith’s effective assertion of per se harmful error. In enacting 5 U.S.C. § 7701, Congress did not intend that agencies be “punished” for nonprejudicial errors they may have committed while attempting to carry out Congress’ mandate “to maintain ‘an effective and efficient Government.’ ” Bureau of Alcohol, Tobacco and Firearms v. Federal Labor Relations Authority, 464 *1546U.S. 89, 92, 104 S.Ct. 439, 441, 78 L.Ed.2d 195 (1983); see Nutt, — U.S. at —, 105 S.Ct. at 2891. “It is insufficient simply to show that a statutory procedure was not followed at the agency level. Harmful error must be shown.” Handy v. United States Postal Service, 754 F.2d 335 (Fed. Cir.1985) (denial of statutory right to oral reply).
Nor, as above indicated, can we accept the Government’s assertion that proceedings before the board, solely because they are “de novo”, must always be seen as having worked a per se cure of any procedural error that may have occurred at the agency level. Were that the case, judicial review of harmful error determinations would be a fruitless enterprise. As this court has stated, a person may have a “better and perhaps dispositive chance” of successfully contesting an adverse action at the agency level. Mercer, 772 F.2d at 860. Though that practical observation does not lessen the employee’s burden of showing harmful error, 5 C.F.R. § 1201.-56(c)(3), it appropriately focuses the attention of the board and the reviewing court on events and possibilities at the agency level.
The statements of Head and Vaughn, which Smith now says he would have been presented at the Step 1 hearing, were presented to the Presiding Official, who accorded them minimal weight. No one has challenged in the briefs filed in this court the first hand, unambiguous, and entirely credible testimony of Officers Con-don and Padro (which was subject to cross-examination before the Presiding Official), nor has counsel for Smith challenged the Presiding Official’s determination that Smith’s testimony was inherently non-credible. Smith has shown us no reason why, had all the evidence presented at the board hearing also been presented at the Step 1 hearing, identical minimal weight would not have been accorded the statements of Smith's witnesses, or why identical credibility determinations would not have been drawn respecting the testimony of Condon, Padro, and Smith.
Smith, who as indicated bears the burden of establishing harmfulness, has not suggested anything that he might have said or done or presented at the predetermination hearing that might have caused a different agency decision. To say, as does Smith, only that the same evidence presented to the board might have been viewed differently by the agency would be to make every error harmful and to require reversal of every board determination that an error was harmless.
Smith proposes that we order him restored to his position in the Postal Service, and award him back pay and promotions, etc., so that the agency may then give him a predetermination hearing before again removing him. That is not required in this case.
The record before us confirms the board’s conclusion that any error present here was harmless. Devine v. Brisco, 733 F.2d 867, 872-73 (Fed.Cir.1984) (“a mere conjectural possibility of prejudice cannot suffice as a basis for inferring actual prejudice”); see also Devine v. White, 697 F.2d 421, 442 (D.C.Cir.1983).
We are unable on this record to conclude that if the testimony and affidavit presented to the presiding official had been presented to the agency at the pretermination stage a different outcome might have been reached, 5 CFR § 1201.56(c)(3), or even that such testimony and affidavit could possibly have affected a change in the agency’s decision. — U.S. at —, 105 S.Ct. at 2890. The error was therefore harmless.
(3) Conclusion
Having determined that Smith has not established a denial of due process or harmful error in the agency’s conduct, we affirm on the basis of the board’s opinion because we do not find that the board’s decision was arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law, or that it was obtained without procedures required by law, rule, or regulation having been fairly followed, or that it was unsupported by substantial evidence. 5 U.S.C. § 7703(c) (1982); see *1547Hayes v. Dept. of the Navy, 727 F.2d 1535, 1537 (Fed.Cir.1984).
AFFIRMED.
. On March 27, 1984, the Postal Service, having sent Smith a Notice of Removal, moved the court for Adjournment in Contemplation of Dismissal of the criminal charges, which charges were eventually dismissed. There is no merit in Smith’s argument that dismissal of the criminal charges weakens the agency’s case for his removal.
. The Postal Service mailed the four Notices of Proposed Removal to Smith and a copy to his union representative on March 20, 1984. It is well-established "that a letter which is properly sealed, stamped, addressed, and deposited in the United States mails is presumed to reach the addressee and be received by him in due course of the mails.” See, e.g., Charlson Realty Co. v. United States, 384 F.2d 434 (Ct.Cl.1967). The union representative obviously received his copy sometime before scheduling the April 3 hearing. Smith asserts that sixteen days transpired between the mailing of the Notices and his receipt of at least one of them. Even today, that is far more than the "due course of the mails.” Inexplicably, however, the agency accepted without challenge Smith’s statement that he did not receive a Notice until April 5, and we must, therefore, do the same.
. The dissenting opinion presents a far more extensive review of the record and a more persuasive set of arguments than those presented by counsel for Smith. The dissenting opinion accepts as facts untested assertions appearing on forms in the record, some of which are significantly different from the facts testified to before the presiding official. For the reason set forth in the text, however, we find unpersuasive the view that a fundamental deprivation of due process or harmful error occurred in this case.
. Smith did not testify as to whether his union representative had told him of the Notice, or why he was denied access, or what time of day or night he went to the building, or who denied him access, or whether others were denied access at the same time.
. We find nothing in the record to suggest that, if the mails had taken four days instead of 16, Smith or his representative would have told a story at the April 3 hearing different from that found so incredible by the presiding official.