tests: also test client submission over smtps://

instead of just smtp:// with STARTTLS.

Opted to call the flag --ssl and not --tls to keep it consistent with
the module option (mailserver.enableSubmissionSsl), dovecot internals
and smtplib in mail-check.py.

scripts/mail-check.py

@@ -12,7 +12,15 @@ RETRY = 100
 
 
 def _send_mail(
-    smtp_host, smtp_port, smtp_username, from_addr, from_pwd, to_addr, subject, starttls
+    smtp_host,
+    smtp_port,
+    smtp_username,
+    from_addr,
+    from_pwd,
+    to_addr,
+    subject,
+    starttls,
+    ssl,
 ):
     print(f"Sending mail with subject '{subject}'")
     message = "\n".join(
@@ -28,9 +36,10 @@ def _send_mail(
     )
 
     retry = RETRY
+    smtp_class = smtplib.SMTP_SSL if ssl else smtplib.SMTP
     while True:
         try:
-            with smtplib.SMTP(smtp_host, port=smtp_port) as smtp:
+            with smtp_class(smtp_host, port=smtp_port) as smtp:
                 try:
                     if starttls:
                         smtp.starttls()
@@ -171,6 +180,7 @@ def send_and_read(args):
         to_addr=args.to_addr,
         subject=subject,
         starttls=args.smtp_starttls,
+        ssl=args.smtp_ssl,
     )
 
     _read_mail(
@@ -206,6 +216,7 @@ parser_send_and_read = subparsers.add_parser(
 parser_send_and_read.add_argument("--smtp-host", type=str)
 parser_send_and_read.add_argument("--smtp-port", type=str, default=25)
 parser_send_and_read.add_argument("--smtp-starttls", action="store_true")
+parser_send_and_read.add_argument("--smtp-ssl", action="store_true")
 parser_send_and_read.add_argument(
     "--smtp-username",
     type=str,