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SENDMAIL EMAIL being rejected by outside ISP

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Matt Mumford
Occasional Advisor

SENDMAIL EMAIL being rejected by outside ISP

Hey all

We use sendmail to send email through our outlook exchange either locally within our domain or to sales reps that may have some various ISP. When we send to Yahoo (for example) there is no problem the email gets there, however ISP(s) like Bellsouth reject the email. I have the DJ entry set to our companies domain. I have the DS entry set to the absolute path of our exchange server and I have the DM set to our domain also. When I send the email to a place I know it will go the header always shows one of the recieved lines saying "user@localhost". Does anyone know if this can cause a problem for some external ISP(s)? If not, anyone have thoughts on why some ISP accept my sendmail emails and some do not. BTW, sprint pcs accepts the emails too. Any thoughts?
2 REPLIES
Geoff Wild
Honored Contributor

Re: SENDMAIL EMAIL being rejected by outside ISP

user@localhost will get denied a lot...anti spam reasons.

Try setting your domain in the DJ macro as well...then restart sendmail....



Rgds...Geoff
Proverbs 3:5,6 Trust in the Lord with all your heart and lean not on your own understanding; in all your ways acknowledge him, and he will make all your paths straight.
Steven E. Protter
Exalted Contributor
Solution

Re: SENDMAIL EMAIL being rejected by outside ISP

My inbound mail server is strict due to abuse.

1) Reject based on reverse lookup not being there.
2) Reject if there is no DNS lookup on the sender. This means if the domain name can't be looked up on the public internet you're mail not grata as far as my mail server goes.

I'm configured in a way that many major ISP's are.

So to fix it you can do one of the following:

set up the Dj directive in sendmail.cf(prior post) restart sendmail as follows after:
/sbin/init.d/sendmail stop
/sbin/init.d/sendmail start

OR

You can set up a DNS entry for this server that resolves the hostname to a fully qualified external domain name.

sendmail will pick up the hostname and use that instead of user@localhost and then you have a chance your mail will get delivered.

This is a ever changing situation. As spammers find new ways to defeat countermeasures, ISP's tighten up the rules. So its a good idea to keep up to date on this stuff.

There is a lot more on this topic at http://www.sendmail.org

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Steven E Protter
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