I am not sure it is greylisting your problem, this is an email rejected by greylist
Feb 3 19:02:35 prometheus rspamd[1742]: <b0febf>; proxy; rspamd_add_passthrough_result: <NM666760DDE5563C048francet_mkt_prod1@nl.la1
ere.fr>: set pre-result to 'soft reject' (no score): 'Try again later' from greylist(1)
Feb 3 19:02:35 prometheus rspamd[1742]: <b0febf>; proxy; rspamd_task_write_log: id: <NM666760DDE5563C048francet_mkt_prod1@nl.la1ere.
fr>, qid: <4EFAB18012AC9>, ip: 82.165.159.39, from: <bounces@nl.la1ere.fr>, (default: F (soft reject): [17.89/19.90] [BAYES_SPAM(5.10
){100.00%;},SPAM_FLAG(5.00){},UNITEDINTERNET_SPAM(5.00){},RBL_SPAMHAUS_SBL(2.00){82.165.159.39:from;},XM_CASE(0.50){},FORGED_SENDER(0
.30){region@nl.la1ere.fr;bounces@nl.la1ere.fr;},BAD_REP_POLICIES(0.10){},MIME_GOOD(-0.10){multipart/alternative;text/plain;},MX_GOOD(
-0.01){cached: a.mx.p4.neolane.net;},ASN(0.00){asn:8560, ipnet:82.165.0.0/16, country:DE;},DKIM_TRACE(0.00){nl.la1ere.fr:+;},DMARC_PO
LICY_ALLOW(0.00){nl.la1ere.fr;none;},DMARC_POLICY_ALLOW_WITH_FAILURES(0.00){},FROM_HAS_DN(0.00){},FROM_NEQ_ENVFROM(0.00){region@nl.la
1ere.fr;bounces@nl.la1ere.fr;},GREYLIST(0.00){greylisted;Mon, 03 Feb 2020 18:07:35 GMT;new record;},HAS_REPLYTO(0.00){contact@nl.la1e
re.fr;},IP_REPUTATION_HAM(0.00){asn: 8560(-0.13), country: DE(-0.00), ip: 82.165.159.39(0.00);},MID_RHS_MATCH_FROM(0.00){},MIME_TRACE
(0.00){0:+;1:+;2:~;},PRECEDENCE_BULK(0.00){},PREVIOUSLY_DELIVERED(0.00){sylvie@domain.org},RCPT_COUNT_ONE(0.00){1;},RCVD_COUNT_T
WO(0.00){2;},RCVD_TLS_LAST(0.00){},REPLYTO_DN_EQ_FROM_DN(0.00){},REPLYTO_DOM_EQ_FROM_DOM(0.00){},R_DKIM_ALLOW(0.00){nl.la1ere.fr:s=ne
olane;},R_SPF_SOFTFAIL(0.00){~all;},TO_DN_NONE(0.00){},TO_MATCH_ENVRCPT_ALL(0.00){}]), len: 78251, time: 421.811ms, dns req: 74, dige
st: <c5d82b1e8a90debba26aedb520245b21>, rcpts: <sylvie@domain.org>, mime_rcpts: <sylvie@domain.org>, forced: soft reject "Try
again later"; score=nan (set by greylist)
as you can see rspamd states what is the module who did the soft reject