configuring sendmail to send mail through relay server in Oracle Linux 7.7

d.s

1/28/23, 12:19 PM

I am configuring my server to use relay server to send mail. I made the following entries in /etc/mail/sendmail.mc

define(`SMART_HOST', `corprelay.example.com')dnl
MASQUERADE_AS(`example.com')dnl
FEATURE(masquerade_envelope)dnl
FEATURE(masquerade_entire_domain)dnl
MASQUERADE_DOMAIN(localhost)dnl
MASQUERADE_DOMAIN(localhost.localdomain)dnl

m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

systemctl restart sendmail

I am getting the following error in maillogs and mails are getting deferred:

Sep 28 08:00:51 ve4-fsdb-l-p01 sendmail[3242]: 18SC0pTv003242: from=ram, size=229, class=0, nrcpts=1, msgid=<[email protected]>, relay=ram@localhost
Sep 28 08:00:51 ve4-fsdb-l-p01 sendmail[3243]: 18SC0peL003243: from=<[email protected]>, size=521, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]
Sep 28 08:00:51 ve4-fsdb-l-p01 sendmail[3242]: 18SC0pTv003242: [email protected], ctladdr=ram (1011/1011), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30229, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (18SC0peL003243 Message accepted for delivery)
Sep 28 08:05:51 ve4-fsdb-l-p01 sendmail[3245]: 18SC0peL003243: timeout waiting for input from corprelay.example.com. during client greeting
Sep 28 08:05:51 ve4-fsdb-l-p01 sendmail[3245]: 18SC0peL003243: to=<[email protected]>, ctladdr=<[email protected]> (1011/1011), delay=00:05:00, xdelay=00:05:00, mailer=relay, pri=120521, relay=corprelay.example.com. [20.11.7.5], dsn=4.0.0, stat=Deferred: Connection timed out with corprelay.example.com.

Note: IPs and hostname are dummy.

Thanks and regards

119

0 + 0

sendmail

Gerald Schneider

1/28/23, 12:54 PM

Timeouts usually point toward firewall issues.

Michael Hampton

1/28/23, 1:16 PM

Your config seems OK. I think it's time to talk to whoever runs corprelay.... and find out if they are firewalling you.

d.s

1/29/23, 6:57 AM

But I am able to telnet to port 25 of the corprelay server.

Score:0

Server

d.s

2/21/23, 11:06 AM

Firewall was blocking the sendmail traffic. Once the firewall rule was in place for port 25, sendmail started working. Surprisingly I was able to telnet on port 25, but I was not able to send the mail using telnet before it was allowed on firewall.

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Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: configuring sendmail to send mail through relay server in Oracle Linux 7.7

TH: การกำหนดค่า sendmail เพื่อส่งเมลผ่านเซิร์ฟเวอร์รีเลย์ใน Oracle Linux 7.7

RO: configurarea sendmail pentru a trimite e-mail prin serverul de releu în Oracle Linux 7.7

RU: настройка sendmail для отправки почты через сервер ретрансляции в Oracle Linux 7.7

VI: định cấu hình sendmail để gửi thư qua máy chủ chuyển tiếp trong Oracle Linux 7.7

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