Your task sends files one by one: one file in each message. It works correctly.
If you want to send all files in folder as attachments in one message, see task below.
;**********************
;* RoboTask Task file *
;* Do not edit! *
;**********************
[Root]
ActionAfterRun=INTEGER|0
Actions=FOLDER
Automat=INTEGER|-1
CatID=INTEGER|565106205
ContinueOnError=INTEGER|0
Events=FOLDER
ExternalName=STRING|"Task357"
Hide=INTEGER|0
ID=INTEGER|1948853370
Name=STRING|"Auto Mail (all files in one message)"
Priority=INTEGER|3
RunOnClose=INTEGER|0
RunOnStartup=INTEGER|0
ToLog=INTEGER|3
[Actions]
Action1=FOLDER
Action2=FOLDER
Action3=FOLDER
Action4=FOLDER
Action5=FOLDER
Action6=FOLDER
[Actions\Action1]
ActionID=STRING|"A_FILE_DELETE"
Enabled=INTEGER|-1
Name=STRING|"Delete File"
Params=FOLDER
[Actions\Action1\Params]
Count=STRING|"1"
deletedirs=STRING|"0"
file0=STRING|"c:\filestosend.txt"
subdir=STRING|"0"
ToRecycleBin=STRING|"0"
[Actions\Action2]
ActionID=STRING|"A_FILE_SEARCH"
Enabled=INTEGER|-1
Name=STRING|"Create File List (c:\filestosend.txt)"
Params=FOLDER
[Actions\Action2\Params]
After=STRING|"0"
aftercount=STRING|"0"
AfterLine=STRING|"0"
Before=STRING|"0"
beforecount=STRING|"0"
BeforeLine=STRING|"0"
createmode=STRING|"1"
date1=STRING|"20051210"
date2=STRING|"20051210"
destfile=STRING|"c:\filestosend.txt"
DuringDays=STRING|"1"
DuringMonths=STRING|"1"
file0=STRING|"C:\testsend\*.*"
filecount=STRING|"1"
OlderDays=STRING|"1"
OlderMonths=STRING|"1"
searchkind=STRING|"0"
subdirs=STRING|"1"
WithoutPath=STRING|"0"
[Actions\Action3]
ActionID=STRING|"A_FLOW_IF"
Enabled=INTEGER|-1
Name=STRING|"If Then"
Params=FOLDER
[Actions\Action3\Params]
case=STRING|"0"
operator=STRING|"3"
type=STRING|"1"
value1=STRING|"{FileSize(c:\filestosend.txt)}"
value2=STRING|"0"
[Actions\Action4]
ActionID=STRING|"A_INET_SENDMAIL"
Enabled=INTEGER|-1
Name=STRING|"Send Email"
Params=FOLDER
[Actions\Action4\Params]
attach0=STRING|"{TextFile(c:\filestosend.txt)}"
attachcount=STRING|"1"
auth=STRING|"0"
from=STRING|"oleg@robotask.com"
host=STRING|"localhost"
html=STRING|"0"
msg0=STRING|"New Incoming PO"
msgcount=STRING|"1"
password=STRING|"2616924690269882519740554"
port=STRING|"25"
subject=STRING|"NEW INCOMING PO"
to=STRING|"oleg@robotask.com"
[Actions\Action5]
ActionID=STRING|"A_FILE_DELETE"
Enabled=INTEGER|-1
Name=STRING|"Delete File"
Params=FOLDER
[Actions\Action5\Params]
Count=STRING|"1"
deletedirs=STRING|"0"
file0=STRING|"{TextFile(c:\filestosend.txt)}"
subdir=STRING|"0"
ToRecycleBin=STRING|"0"
[Actions\Action6]
ActionID=STRING|"A_FLOW_ENDIF"
Enabled=INTEGER|-1
Name=STRING|"End If"
[Events]
Event1=FOLDER
[Events\Event1]
Enabled=INTEGER|-1
EventID=STRING|"E_GENERAL_CYCLIC"
Params=FOLDER
[Events\Event1\Params]
id=STRING|"A1QTGG0E"
interval=STRING|"20"