Author: Martin Fischer Date: To: exim-users Subject: [exim] MS 365 "X-Matching-Connectors" header bounce error
Hello,
I would need your help. Messages from Exim to some MS 365 accounts hosted in Europe are bouncing when sent from MS Outlook or an Android client. Sending same message from Webmail (Roundcube) messages´is delivered but X-Matching-Connectors header is very big.
2021-12-09 14:07:23 1mvK4y-007pOT-RQ <= contact@??? H=(XXXXX) [XXXXXXXX]:62544 P=esmtpsa X=TLS1.2:ECDHE-ECDSA-AES128-GCM-SHA256:128 CV=no A=dovecot_login:contact@??? S=1216 id=!&!AAAAAAAAAAAuAAAAAAAAAGMiling04JAkZp
JJsnUSnoBAMO2jhD3dRHOtM0AqgC7tuYAAAAAAA4AABAAAACL2Fs9vGAsTbjJEYiyeee1AQAAAAA=@atvirtual.nl T="MS Mail Bounce Report Verification" for postmaster@???
2021-12-09 14:07:23 1mvK4y-007pOT-RQ SMTP connection outbound 1639058843 1mvK4y-007pOT-RQ atvirtual.nl postmaster@???
2021-12-09 14:07:25 1mvK4y-007pOT-RQ ** postmaster@??? R=dkim_lookuphost T=dkim_remote_smtp H=xxxxxx01b.mail.protection.outlook.com [104.47.17.138] X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=yes: SMTP error from remote mail ser
ver after end of data: 554 5.6.211 Invalid MIME Content: Single text value size (32799) exceeded allowed maximum (32768) for the 'X-Matching-Connectors' header. [VI1PR0202MB2528.eurprd02.prod.outlook.com] [AS9PR06CA0096.eurprd06.prod.outl
ook.com] [VI1EUR05FT058.eop-eur05.prod.protection.outlook.com]
MS 365 support: "We have analyzed the SMTP logs collected from senders and we have discussed this with SEE. As per the logs the issue is from sender's end and not from Microsoft's end."
