1 diff --git a/src/transports/smtp.c b/src/transports/smtp.c
2 index 59abb9ef8..ad648755f 100644
3 --- a/src/transports/smtp.c
4 +++ b/src/transports/smtp.c
5 @@ -5059,7 +5053,8 @@ if (max_received_linelength > ob->message_linelength_limit)
6 addr->transport_return = PENDING_DEFER;
8 set_errno_nohost(addrlist, ERRNO_SMTPFORMAT,
9 - US"message has lines too long for transport", FAIL, TRUE, &now);
10 + string_sprintf("message has lines too long for transport (received line length %d while limit is %d)",
11 + max_received_linelength, ob->message_linelength_limit), FAIL, TRUE, &now);