SMTP email to different hosts


I am trying to send an email to people in our company and also in other company once I finish a task. I am using SMTP client to send the email. But, people in the other company are not getting the emails. Can I use SMTP client to send emails to different domains(hosts)?

Dim SMTPMail As SmtpClient
Dim Body As String = ""
Dim Subject As String
Dim m_MailFrom =
Dim m_MailRec =,,
SMTPMail = New SmtpClient
SMTPMail.Send(m_MailFrom, m_MailRec, Subject, Body)

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what are you using for the smtp relay?
Your email server may not allow relaying outside your company.  To test this, telnet to your email server with these commands....

telnet x.x.x.x 25

mail from:<ValidUser@InternalDomain>
rcpt to:<User@ExternalDomain>

If it rejects the rcpt to: command line, you can't relay outside.
You also need to do this from the computer you are sending the mail from.  Your email server may also restrict relaying to specific computers.

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blitzzyAuthor Commented:
I tested the telnet and everything worked fine.(It did not reject the recipient). I was checking again to make sure that there isnt anything that I missed. This is what I found out:
The "from" address in my code was: "" which is like a default address. There was no such mailbox in our system with that account. We created an actual mailbox called and tried to send the emails to different hosts now and It works great now.
Thanks for your help,
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