merge #12283: Fixed regression in smtplib quoting of leading dots in DATA.

diff --cc Lib/smtplib.py
Simple merge

diff --cc Lib/test/test_smtplib.py
Simple merge

diff --cc Misc/NEWS
index 95626462675b35d457273e47b8129836b71dd65d,dab5355eddb7c936dcfba4630143f223a41c82cd..f422b2ddf53b339db2eeb13618bde334524040d8
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -187,9 -22,8 +187,11 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #12283: Fixed regression in smtplib quoting of leading dots in DATA.
+ 
 +- Issue #10424: Argparse now includes the names of the missing required
 +  arguments in the missing arguments error message.
 +
  - Issue #12168: SysLogHandler now allows NUL termination to be controlled using
    a new 'append_nul' attribute on the handler.