Hi, we're using a multi-server setup (3.1.3) with a dedicated email server, on aws. rDNS for the mailserver is correctly configured by amazon. mailforwards have been working fine, up till this week, when any mailforwards to btinternet have started being rejected. we are gettings mails from eg [email protected] to [email protected], which are to be forwarded to [email protected] which now results in the following in our postfix logs: Sep 22 09:43:10 smtp postfix/smtp: 58FB1460C1: to=<[email protected]>, orig_to=<[email protected]********s.co.uk>, relay=mx.bt.lon5.cpcloud.co.uk[184.108.40.206]:25, delay=235673, delays=235672/0.01/0.45/0.5, dsn=4.0.0, status=deferred (host mx.bt.lon5.cpcloud.co.uk[220.127.116.11] said: 421 Too many messages (18.104.22.168) on 2017/09/22 09:43:10 BST from un-validated IP address: 22.214.171.124. Please add a SPF record for the domain pepperrabbitmusic.com to your DNS or ask your Broadband Provider / Domain Registrar to do this, we will be unable to deliver email until this is done due to the volume of email being sent from this IP address. Guide for bulk senders www.bt.com/bulksender (in reply to MAIL FROM command)) where in this case peterrabbitmusic.com is sending mail to [email protected] on our server to be forwarded to ***@btinternet.com the spf record for the localdomain. is 'v=spf1 +a +mx +ip4:<ip address> -all' and the mx records are localdomain. MX 10 smtp.scl.co.uk. and localdomain. MX 50 mail.scl.co.uk. the master.cf file has: smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) where both myhostname and mail_name resolve to smtp.scl.co.uk and in the dns for scl.co.uk , mail.scl.co.uk is a cname to smtp.scl.co.uk is this just btinternet playing silly buggers? do I need to install/configure SRS, is there anything that can be done within the ispconfig control panel? https://serverfault.com/questions/82234/srs-sender-rewriting-when-forwarding-mail-through-postfix thanks lee.