have been battling with my sendmail on redhat 8.0.

My first problem was items were going out as localhost.localdomain

now I got them going out as davesbedroom.com and that works good..

Everything works fine with the nodes that use Microsoft outlook pop3 with the server.

Problem is that the scripts that use '/usr/lib/sendmail -oi -t'

I get this error when it times out
"Jun 25 14:21:33 gateway sendmail[6221]: h5PJIOM3006221: to=dave@davesbedroom.com, ctladdr=root (0/0), delay=
00:03:09, xdelay=00:03:09, mailer=relay, pri=90123, relay=localhost.com. [10.11.12.13], dsn=4.0.0, stat=Deferred: Connection timed out with localhost.com."

Why is the email trying to go to localhosts.com? why does it work fine with pop3 and Microsoft outlook and not with sendmail at the command line!!

post your sendmail.mc file here located in /etc/mail i think (or do an slocate on semdmail.mc)

divert(-1)
dnl This is the sendmail macro config file. If you make changes to this file,
dnl you need the sendmail-cf rpm installed and then have to generate a
dnl new /etc/mail/sendmail.cf by running the following command:
dnl
dnl m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
dnl
include(`/usr/share/sendmail-cf/m4/cf.m4')
VERSIONID(`linux setup for Red Hat Linux')dnl
OSTYPE(`linux')
dnl Uncomment and edit the following line if your mail needs to be sent out
dnl through an external mail server:
dnl define(`SMART_HOST',`smtp.your.provider')
define(`confDEF_USER_ID',``8:12'')dnl
undefine(`UUCP_RELAY')dnl
undefine(`BITNET_RELAY')dnl
dnl define(`confAUTO_REBUILD')dnl
define(`confTO_CONNECT', `1m')dnl
define(`confTRY_NULL_MX_LIST',true)dnl
define(`confDONT_PROBE_INTERFACES',true)dnl
define(`PROCMAIL_MAILER_PATH',`/usr/bin/procmail')dnl
define(`ALIAS_FILE', `/etc/aliases')dnl
define(`STATUS_FILE', `/etc/mail/statistics')dnl
define(`UUCP_MAILER_MAX', `2000000')dnl
define(`confUSERDB_SPEC', `/etc/mail/userdb.db')dnl
define(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnl
define(`confAUTH_OPTIONS', `A')dnl
dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
dnl define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
dnl define(`confCACERT_PATH',`/usr/share/ssl/certs')
dnl define(`confCACERT',`/usr/share/ssl/certs/ca-bundle.crt')
dnl define(`confSERVER_CERT',`/usr/share/ssl/certs/sendmail.pem')
dnl define(`confSERVER_KEY',`/usr/share/ssl/certs/sendmail.pem')
dnl define(`confTO_QUEUEWARN', `4h')dnl
dnl define(`confTO_QUEUERETURN', `5d')dnl
dnl define(`confQUEUE_LA', `12')dnl
dnl define(`confREFUSE_LA', `18')dnl
define(`confTO_IDENT', `0')dnl
dnl FEATURE(delay_checks)dnl
FEATURE(`no_default_msa',`dnl')dnl
FEATURE(`smrsh',`/usr/sbin/smrsh')dnl
FEATURE(`mailertable',`hash -o /etc/mail/mailertable.db')dnl
FEATURE(`virtusertable',`hash -o /etc/mail/virtusertable.db')dnl
FEATURE(redirect)dnl
FEATURE(always_add_domain)dnl
FEATURE(use_cw_file)dnl
FEATURE(use_ct_file)dnl
dnl The '-t' option will retry delivery if e.g. the user runs over his quota.
FEATURE(local_procmail,`',`procmail -t -Y -a $h -d $u')dnl
dnl FEATURE(`access_db',`hash -T<TMPF> -o /etc/mail/access.db')dnl
FEATURE(`access_db')dnl
FEATURE(`blacklist_recipients')dnl
MASQUERADE_AS(davesbedroom.com)dnl
EXPOSED_USER(`root')dnl
dnl This changes sendmail to only listen on the loopback device 127.0.0.1
dnl and not on any other network devices. Comment this out if you want
dnl to accept email over the network.
dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')
dnl NOTE: binding both IPv4 and IPv6 daemon to the same port requires
dnl a kernel patch
dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')
dnl We strongly recommend to comment this one out if you want to protect
dnl yourself from spam. However, the laptop and users on computers that do
dnl not have 24x7 DNS do need this.
dnl FEATURE(`accept_unresolvable_domains')dnl
dnl FEATURE(`relay_based_on_MX')dnl
MAILER(smtp)dnl
MAILER(procmail)dnl
Cwlocalhost.localdomain

I am pretty sure noone knows the answer to this question. I have looked all over the interweb and have noticed that its just a glitch that noone knows how to fix or explain. I am going to install redhat9 real quick tonite.. I have been putting it off. Now I have some bigger hard drives to stuff in the case :-)

I had same problem apparently. I worked on it many days and nights. Tried both Postfix and sendmail, all the mail goes to /etc/mail/clientmqueue, and give message "Deffered: Connection timed out with localhost.com".

I changed /etc/hosts file. It had one line like this:
127.0.0.1 localhost
changed to:
127.0.0.1 localhost localhost.localdomain.
What it does is just adding localhost.localdomain as alias of localhost. I assume that if you change the last line in sendmail.mc "Cwlocalhost.localdormain" to "Cwlocalhost" might also works.
I know it's very late to answer the original post, but, there are maybe many people out there have same problem and searching for a solution. This post might save some sleepless nights in some cases.