SMTP settings give 550 Unexpected response from SMTP server during handshake.
 

I've been trying to set up the SMTP settings within vBulletin email settings. Regardless of what settings/ports I use for non-encrypted, SSL or TSL, I always get:

PHP User Warning: 550 Unexpected response from SMTP server during handshake in ..../includes/class_mail.php on line 715

Now, I asked my mail provider to look into it further, and replied that the ACL triggered. And asked why the application is using HELO statement?

This is beyond my knowledge. Anyone happens to know?

Regards,
Skyrider

Your server sends the helo, not vbulletin, its a server issue.

What smtp server are your trying to connect to?

Is this a dedicated server your site is on?

I'm trying to connect to one of the MXRoute mail servers. (In this case, arrow.mxrouting.net). I wasn't aware that it was a server side issue, as I assumed SMTP connection goes directly through vBulletin. It's a Root server (mix between VPS and Dedicated), so ya.. I can adjust the mail settings on my server.

But even if I disable the "sendmail" which is installed on my server, still getting the same error. Postfix is not even installed.

Or this something within the server settings itself, or its mail application settings?

I'd like to point out that Xenforo has no issues sending out SMTP emails, vBulletin is the only one throwing out errors. So are you sure it's not vBulletin's fault?

Most large ISP's require valid HELO's from the server connecting to them.

Without looking at the server & the actual issue, im still going to lay blame on the mail/server, not vb itself.

But this is related to your hostname, so without seeing all the settings on the server, its hard to say which program is at fault, but im still stating its not VB.

I'm not using any mail applications on my server though, and as I mentioned above. Xenforo has no problems connecting to the same SMTP information. So it's weird that XF works, while vBulletin doesn't.

SMTP is how you are sending it, not how youre creating it, so yes you still use a mail program to generate it.