The mails sent by weblate originate from an IP address block that was unfortunately blocked.
Aug 28 19:55:19 weblate postfix/smtp: DF82B4A74A: to=, relay=spool.mail.gandi.net[184.108.40.206]:25, delay=0.39, delays=0.01/0.02/0.35/0.02, dsn=5.7.1, status=bounced (host spool.mail.gandi.net[220.127.116.11] said: 554 5.7.1 Service unavailable; Client host [18.104.22.168] blocked using pbl.spamhaus.org; https://www.spamhaus.org/query/ip/22.214.171.124 (in reply to RCPT TO command))
I went ahead and asked for removal. Got confirmations right now that this is in progress. It will take 30 minutes to complete but I don’t know how long it will take for gandi or other mail servers to update.