I have my smtp server -- smtp.drdb.com which is registered in DNS. I need to setup Mutt utility in my RHEL 6 server. Where should I input my smtp server details in mutt.rc file so that I can send mail. When I try to send mail from mutt, it goves me error Invalid URL - smtp.drdb.com
If you use a version of mutt that is compiled with SMTP support then mutt can send mail to another server via SMTP. Otherwise it will always use the local mail server.
To use it, you have to set the
smtp_url Type: string Default: “” Defines the SMTP smarthost where sent messages should relayed for delivery. This should take the form of an SMTP URL, e.g.: smtp[s]://[user[:pass]@]host[:port] where “[...]” denotes an optional part. Setting this variable overrides the value of the $sendmail variable.
Just to complement the original answer - in order to set external SMTP server you need to add following line either to /etc/Muttrc (for system-wide configuration) or ~/.muttrc (for user configuration):
set smtp_url = "smtp[s]://[user[:pass]@]host[:port]"
where host is your SMTP server, and as said in the original answer everything inside  is optional...
set smtp_url = "smtp://gmailusername:firstname.lastname@example.org:587"– RedomanOct 19, 2022 at 16:20
The actual sending of mail is traditionally delegated to an external program like
sendmail, mutt does not connect to SMTP directly itself. If sendmail is too much for you, you can consider using something like
msmtp for a simple delivery mechanism to an SMTP server, the actual SMTP server is then configured in a simple
~/.msmtprc configuration. Consult the documentation (
2Mutt is capable of connecting to an SMTP server. See
smtp_urlas described in another answer. Sep 26, 2015 at 12:19