CREATE OR REPLACE TRIGGER "TEST_SCHEMA"."TS_TESTTABLE_T_INSERT" BEFORE INSERT ON TS_TESTTABLE_T
FOR EACH ROW
  declare 
    v_testchar varchar2;
begin
IF :new.ID is null
   THEN select TS_TESTTABLE_T_ID_SEQ.nextval into :new.ID from dual;
END IF;
IF :new.REF is null or instr(upper(:NEW.REF),'XX')!=0
   THEN 
  begin
  v_testchar := :new.REF;
   select 'BA'||ltrim(to_char(TS_TESTTABLE_T_REF_SEQ.nextval,'000000')) into :new.REF from dual;
   mailout(' "emailSender" ','recipient@email.com','ccRecipient@email.com','Subject line' , 'Body of the email',:v_testchar,:new.REF);
   end;
END IF;

end; 
/

Warning: execution completed with warning
TRIGGER "TEST_SCHEMA"."TS_TESTTABLE_T_INSERT" Compiled.

INSERT into TS_TESTTABLE_T (EMAIL, OWNER_FST_NM, OWNER_SUR_NM)
VALUES('someEmail@email.com','firstname','surname');

Error starting at line 1 in command:
INSERT into TS_TESTTABLE_T (EMAIL, OWNER_FST_NM, OWNER_SUR_NM)  
VALUES('someEmail@email.com','firstname','surname')  
Error at Command Line:1 Column:12
Error report:
SQL Error: ORA-04098: trigger 'TEST_SCHEMA.TS_TESTTABLE_T_INSERT' is invalid and failed re-validation
04098. 00000 -  "trigger '%s.%s' is invalid and failed re-validation"
*Cause:    A trigger was attempted to be retrieved for execution and was
           found to be invalid.  This also means that compilation/authorization
           failed for the trigger.
*Action:   Options are to resolve the compilation/authorization errors,
           disable the trigger, or drop the trigger.

 v_testchar := :new.REF;

v_testchar varchar2;

SQL> declare
  2  x varchar2;
  3  begin
  4  x:='test';
  5  end;
  6  /
x varchar2;
  *
ERROR at line 2:
ORA-06550: line 2, column 3:
PLS-00215: String length constraints must be in range (1 .. 32767)

SQL> 

SQL> create or replace trigger trg_dept
  2    before insert on dept
  3    for each row
  4  declare
  5    v_testchar varchar2;
  6  begin
  7    null;
  8  end;
  9  /

Warning: Trigger created with compilation errors.

SQL> show err
Errors for TRIGGER TRG_DEPT:

LINE/COL ERROR
-------- -----------------------------------------------------------------
2/14     PLS-00215: String length constraints must be in range (1 ..
         32767)

SQL>

SQL> l5
  5*   v_testchar varchar2;
SQL> c/varchar2/varchar2(20)
  5*   v_testchar varchar2(20);
SQL> /

Trigger created.

SQL>

SQL> create or replace procedure my_test
  2  is
  3    v_testvar varchar2;
  4  begin
  5    select :v_testvar into v_testvar from dual;
  6  end;
  7  /

Warning: Procedure created with compilation errors.

SQL> show error
Errors for PROCEDURE MY_TEST:

LINE/COL ERROR
-------- -----------------------------------------------------------------
5/10     PLS-00049: bad bind variable 'V_TESTVAR'