Just as a long outstanding note.
I made an extension to EnsLib.FTP.OutboundAdapter that adds handling for Use Session Resumption as a parameter, but it appears as of the 2024 version of IRIS this has been added to the core IRIS code.

We've only recently been able to use it as we had an old OpenSSL version that did not support the flags required, so this has been left and not looked at in a few years.

For reference the extension I wrote is listed below:

 Include Ensemble Class Custom.Operations.FTP.OutboundAdapter Extends EnsLib.FTP.OutboundAdapter [ ClassType = "", Inheritance = right, ProcedureBlock, System = 4 ]
{ Property SSLUseSessionResumption As %Boolean [ InitialExpression = 0 ]; /// These properties can be configured or set by the associated Business Operation
Parameter SETTINGS = "SSLUseSessionResumption:Connection"; /// Connect to the FTP server and log in, setting the directory and transfer mode
Method Connect(pTimeout As %Numeric = 30, pInbound As %Boolean = 0) As %Status
{
Set $ZT="Trap", tSC=$$$OK, tFTPPort=..FTPPort
Do {
If ..Connected { Do ..TestConnection(pInbound) Quit:..Connected } #; Connect to the FTP server
If '$IsObject(..%CredentialsObj) Do ..CredentialsSet(..Credentials) If '$IsObject(..%CredentialsObj) { Set tSC=$$$ERROR($$$EnsErrNoCredentials,..Credentials) Quit }
Set ..%LastSetFilePath="" #; find FTP type; get a configuration-settings instance, use it to open an FTP Session instance
  If ..%isSFTP {
  #; Connect using an SFTP object
Set:""=tFTPPort tFTPPort=22
Set tIOAddr=..FTPServer_":"_tFTPPort_"/"_..Credentials_"/SSL='"_..SSLConfig_"'/PubKey='"_..SFTPPublicKeyFile_"'/PrivKey='"_..SFTPPrivateKeyFile_"'"
$$$catTRACE("connwait","Connecting to "_tIOAddr_"/"_..Credentials_"'/PubKey='"_..SFTPPublicKeyFile_"'/PrivKey='"_..SFTPPrivateKeyFile_"' with timeout="_pTimeout)
  Set:'$IsObject(..FTP)||'..FTP.%Extends("EnsLib.FTP.CommonSSH") ..FTP=$this
            Set ..FTP.SSLUseSessionResumption=..SSLUseSessionResumption
  Set t0=$zh
  Set tSC=..FTP.ConnectSSH(pTimeout, pInbound, tFTPPort)
  } Else {
  #; Connect using standard FTP, or FTPS with SSLConfig
Set:""=tFTPPort tFTPPort=21
Set tIOAddr=..FTPServer_":"_tFTPPort_"/"_..Credentials_"/SSL='"_..SSLConfig
$$$catTRACE("connwait","Connecting to "_tIOAddr_"/"_..Credentials_" with timeout="_pTimeout)
  Set:'$IsObject(..FTP)||'..FTP.%Extends("%Net.FtpSession") ..FTP=##class(%Net.FtpSession).%New()
            Set ..FTP.SSLUseSessionResumption=..SSLUseSessionResumption
Set t0=$zh, ..FTP.Timeout=pTimeout, ..FTP.UsePASV=..UsePASV, ..FTP.LegacySSL=("*"=$E(..SSLConfig,*)), ..FTP.SSLConfiguration=$S("*"=$E(..SSLConfig,*):$E(..SSLConfig,1,*-1),1:..SSLConfig)
If (..FTP.SSLConfiguration'="") {
Set ..FTP.SSLCheckServerIdentity = ..SSLCheckServerIdentity
Set ..FTP.SSLUseSessionResumption = ..SSLUseSessionResumption
}
If '..FTP.Connect(..FTPServer,..%CredentialsObj.Username,..%CredentialsObj.Password,tFTPPort) {
Set tSC=$$$ERROR($$$EnsErrFTPConnectFailed,tIOAddr_"/"_..Credentials,..FTP.ReturnMessage,..FTP.ReturnCode)
}
#; Set after connect since FTP class will query server if empty string
Set ..FTP.CommandTranslateTable = ..CommandTranslateTable
  }
If $$$ISERR(tSC) {
Set tSC=$S((-1'=pTimeout)&&(t0+pTimeout<=$zh): $$$ADDSC($$$ERROR($$$EnsErrOutConnectExpired,pTimeout,$S(..%isSFTP:"SFTP",1:"FTP"),tIOAddr),tSC)
 , 1: $$$ERROR($$$EnsErrOutConnectFailed,$$$StatusDisplayString(tSC),$S(..%isSFTP:"SFTP",1:"FTP"),tIOAddr))
Set ..FTP=$$$NULLOREF
Quit
}
#; Get the system declaration from the FTP server
Set ..%Syst=""  Set:..FTP.System(.tSystem) ..%Syst=tSystem
If ""'=..%Syst {
Set ..%isVMS = ("VMS " = $E(..%Syst,1,$L("VMS ")))
$$$catTRACE("connwait","Detected FTP server system type '"_..%Syst_"'")
}
#; Set the current directory
Set ..%LastSetFilePath=..fixSvrPath(..FilePath,0)
If ""=..%LastSetFilePath {
$$$catTRACE("connwait","Not setting FTP working directory because FilePath is empty")
} Else {
If ..FTP.SetDirectory(..%LastSetFilePath) {
$$$catTRACE("connwait","Set FTP working directory to "_..%LastSetFilePath)
} Else {
Set tSC=$$$ERROR($$$EnsErrFTPDirectoryChangeFailed,..%LastSetFilePath,..FTP.ReturnMessage,..FTP.ReturnCode) 
Set ..%LastSetFilePath=""
Quit
}
}
#; Set the transfer mode
Set tTable = "RAW"
Set csetlc=$ZCVT(..Charset,"L")
Set tAscii=$Case($E(csetlc,1,5),"":1,"defau":1,"ascii":1,"latin":1,"iso-8":1,"utf-8":1,:0)
If 'tAscii {
If '..FTP.Binary() {
Set tSC=$$$ERROR($$$EnsErrFTPModeChangeFailed,"Binary",..FTP.ReturnMessage,..FTP.ReturnCode)
Set ..FTP.TranslateTable = ""
Quit
}
If "binary"'=csetlc {
Set tEnc=..Charset   Set:"*"=$E(tEnc) $E(tEnc)=""
Set tTable = ##class(%IO.I.TranslationDevice).GetCharEncodingTable(tEnc)
Set:tTable="" tTable="RAW"
}
} Else {
If '..FTP.Ascii() {
Set tSC=$$$ERROR($$$EnsErrFTPModeChangeFailed,"Ascii",..FTP.ReturnMessage,..FTP.ReturnCode)
Quit
}
If "ascii"'=csetlc {
If $Case(csetlc,"":0,"default":0,"native":0,:1) {
Set tTable = ##class(%IO.I.TranslationDevice).GetCharEncodingTable(..Charset)
} Else { Set tTable = "" }
Set:tTable="" tTable=$$DefIO^%NLS(5)
}
}
#; Success
Set ..FTP.TranslateTable = tTable
Set tTxt="Connected to FTP Server '"_tIOAddr_"' at path '"_..%LastSetFilePath_"' using Credentials '"_..Credentials_"'"
If ..StayConnected<0 { $$$LOGINFO(tTxt) }
Else {
If pInbound&&'..StayConnected { $$$catTRACE("connwait",tTxt) }
ElseIf ..%logTransfers { $$$LOGINFO(tTxt) }
Else { $$$sysTRACE(tTxt) }
}
Set ..Connected=1
$$$ASSERT(..FTP.Connected)
If (..BusinessHost.%LastReportedError [ "ERROR <Ens>ErrOutConnect")
 ||(..BusinessHost.%LastReportedError [ ..%LastNetErr) {
Set ..BusinessHost.%LastReportedError=""
$$$SetHostMonitor(..BusinessHost.%ConfigName,$$$eMonitorStatus,"OK")
}
Set ..%LastNetErr="%%%%%"
Set i%%IOAddr=tIOAddr
} While 0
Exit
If $$$ISERR(tSC) {
$$$ASSERT('..Connected)
Do:..FTP.Connected ..FTP.Logout() ; force FTP class into sync in case it made a mistake
}
Quit tSC
Trap
Set $ZT="",tSC=$$$EnsSystemError
Set tSC =$$$ERROR($$$EnsErrOutConnectException,$$$StatusText(tSC),$S(..%isSFTP:"SFTP",1:"FTP"),tIOAddr_"/"_..Credentials)
Goto Exit
} }

For those interested. We copied part of the validation check, and updated with some options to truncate as per the schema.

It can be called with:

set tSC = ##class(User.Hl7RangeCheck).RangeChk(.pRequest)

Include EnsHL7

Class User.Hl7RangeCheck
{ ClassMethod RangeChk(ByRef pMsg As EnsLib.HL7.Message) As %Status
{
#dim pIndex as %Integer = 1
Set tSC=$$$OK , tSC2=$$$OK, tSC1=$$$OK
for 
{
set pSeg = pMsg.GetSegmentAt(pIndex)
quit:($ZSTRIP(##class(%String).LogicalToDisplay(pSeg), "<>W" ) = "") quit:(pSeg.Name = "") //$$$ERROR($$$EnsErrGeneral, "Cannot validate segment schemas without a segment name. Unable to validate segment "_$get(pSegNum)_".")
set hasSegNum = 1 - ($get(pSegNum)="")
quit:(pSeg.DocTypeCategory = "") //$$$ERROR($$$EnsErrGeneral, "Cannot validate segment schemas without a category. Unable to validate segment "_$S(hasSegNum:pSegNum_":",1:"")_pSeg.Name_".")
quit:($get($$$vaSchemaGbl(pSeg.DocTypeCategory, "SS", pSeg.Name)) = "") //$$$ERROR($$$EnsErrGeneral, "Unable to retrieve the schema to validate segment against. Unable to validate segment "_$S(hasSegNum:pSegNum_":",1:"")_pSeg.Name_".")
set schema = $$$vaSchemaGbl(pSeg.DocTypeCategory, "SS", pSeg.Name)
for fieldNum=1:1:$listlength(schema)
{
quit:(fieldNum > pSeg.Count)
set fieldDat = pSeg.GetValueAt(fieldNum, pSeg.Separators, .tSC2)
if ($$$ISERR(tSC2))
{
set tSC = $$$ADDSC(tSC, $$$ERROR($$$EnsErrGeneral, "Unable to retrieve field "_fieldNum_" from segment "_$S(hasSegNum:pSegNum_":",1:"")_pSeg.Name_"."))
quit ; can only continue with this field if no error in getting it
}
set fieldSchema = $listget(schema, fieldNum)
if '(((pSeg.Name = "MSH") || (pSeg.Name = "BHS") || (pSeg.Name = "FHS")) && ((fieldNum = 1) || (fieldNum = 2)))
{
set dat = $tr(fieldDat, pSeg.Separators, "") ; remove separators from field
}
else 
{
set dat = fieldDat
}
set data = (dat '= "") ; is anything left?
if (data)
{
//if not data structures, components, subcomponents, datatypes, and/or code tables
if ($listget(fieldSchema, 1) = "")
{ set len = $length(fieldDat)
if (($listget(fieldSchema, 4) '= "") && (len > $listget(fieldSchema, 4))) ; over length restriction
{
if '(((pSeg.Name = "MSH") || (pSeg.Name = "BHS") || (pSeg.Name = "FHS")) && (fieldNum = 2))
{
for rep=1:1:($length(fieldDat, pSeg.RS))
{
if ($length($p(fieldDat, pSeg.RS, rep)) > $listget(fieldSchema, 4))
{ 
set tSC = pMsg.SetValueAt(..Truncate(pMsg.GetValueAt(pSeg.Name_":"_fieldNum_"("_rep_")"),$listget(fieldSchema, 4)) , pSeg.Name_":"_fieldNum_"("_rep_")")
}
}
} }
}
else 
{
k info
set info("SegName") = pSeg.Name , info("fieldNum") = fieldNum, info("sep") = pSeg.Separators
set (info("rep"), info("comp"), info("subComp")) = 1
set:(hasSegNum) info("SegNum") = pSegNum
set info("hasSegNum") = hasSegNum if ($listget(fieldSchema, 1) '= "") ; there is a data structure for the field
{
set dataStruct = $listget(fieldSchema, 1)
set tSC = ..ValidateFieldDataStructure(.pMsg,fieldDat, dataStruct, .info)
}
}
}
} set pIndex = pIndex+1
}
return tSC
} ClassMethod ValidateFieldDataStructure(ByRef pMsg As EnsLib.HL7.Message, field As %String, struct As %String, ByRef info) As %Status [ Internal ]
{
set tSC = $$$OK, error = 0
set category = $p(struct, ":", 1)
set dataStruct = $p(struct, ":", 2)
quit:((category = "") || (dataStruct = "")) $$$ERROR($$$EnsErrGeneral, "Cannot find schema for data structure "_struct_". Unable to validate segment "_$S($get(info("SegNum"))'="":info("SegNum")_":",1:"")_info("SegName")_" field "_info("fieldNum")_" against this structure.")
set structure = $get($$$vaSchemaGbl(category, "DT", dataStruct))
quit:('$data(structure)) $$$ERROR($$$EnsErrGeneral, "Cannot find schema for data structure "_struct_". Unable to validate segment "_$S(info("hasSegNum"):info("SegNum")_":",1:"")_info("SegName")_" field "_info("fieldNum")_" against this structure.") if '(((info("SegName") = "MSH") || (info("SegName") = "BHS") || (info("SegName") = "FHS")) && (info("fieldNum") = 2))
{
for info("rep") = 1:1:$length(field, $$$RSSEP(info("sep")))
 {
set repeat = $piece(field, $$$RSSEP(info("sep")), info("rep"))
for info("comp")=1:1:$length(repeat, $$$CSSEP(info("sep")))
{
quit:(info("comp") > $listlength(structure))
set component = $piece(repeat, $$$CSSEP(info("sep")), info("comp"))
set dat = $tr(component, $$$SSSEP(info("sep"))) ; remove separators from field
set data = (dat '= "") ; is anything left?
if (data)
{
set len = $length(component)
if (($listget($listget(structure, info("comp")),3)'="") && (len > $listget($listget(structure, info("comp")),3))) ; over length restriction
{ 
set tSC = pMsg.SetValueAt(..Truncate(component,$listget($listget(structure, info("comp")),3)), info("SegName")_":"_info("fieldNum")_"("_info("rep")_")"_"."_info("comp"))
}
}
}
}
}
Return tSC
} ClassMethod Truncate(pString As %String, pNum As %Integer) As %String
{
#dim tString As %String = pString If ($LENGTH(pString) > pNum)
{
Set tString = $EXTRACT(pString,1,pNum)
} Return tString
} }