I have configured sendmail using a procedure described in below : Configure Sendmail to Relay Emails through Gmail SMTP.

https://tecadmin.net/sendmail-to-relay-emails-through-gmail-stmp/.

It works but it takes a loooong time , almost a minute to run and send the mail. Is this something caused by a wrong configuration or any other issue ? Any tip on how to make it faster ? Thank you very much!
Any one has experience using zoho mail with digital Ocean ?
Thank you!

Some additional info :

2) Configure Sendmail with SMART_HOST

Now add following configuration lines into your sendmail.mc configuration file below “MAILER” definition.

 define(`SMART_HOST',`[smtp.gmail.com]')dnl
 define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
 define(`ESMTP_MAILER_ARGS', `TCP $h 587')dnl
 define(`confAUTH_OPTIONS', `A p')dnl
 TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
 define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
 FEATURE(`authinfo',`hash -o /etc/mail/authinfo/smtp-auth.db')dnl

In the next step we will need to re-build sendmail’s configuration. To do that execute:

make -C /etc/mail

3) Verify Setup

After completing all the above configuration’s, reload the sendmail service to apply changes.

sudo service sendmail reload