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EMail Sending rate for open source EMail Server

I am setting up an outgoing email gateway.

I need to send millions of emails every single month to our company customers. I can schedule these emails to be sent in waves , I mean I can throttle their rate every minute/hour over number of days/weeks. I know a spike in sending email could be treated as a Spambot.
I looked at Amazon SES /Mandrill and that comes out to be very expensive. My emails will be mainly marketing emails and won't have attachments. Majority of these emails are sent to existing customers so this not a SPAM and shouldn't be treated like that by ISPs.

I am inclined to set up servers by myself using a cheap hosting options.

Can someone roughly calculate how many emails one could send over week/month if I have 10MBPS connectivity to outside world?
Let's say every email is around 50KB in size.

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2 Solutions
Dave BaldwinFixer of ProblemsCommented:
SPAM is what the receiver says it is.  The 'official' definition is unWanted emails, no matter what the subject or relationship.  The choice is theirs, not yours.

Before you try to set up your own server, check with your ISP and see how many emails they will allow you to send each day or hour.  Limits typically range from 25 per hour to 5000 per day.  At 5000 per day, it will take 200 days to send a million emails.

You will never get to use your full bandwidth to send email.  Sending email involves a back and forth negotiation with each and every mail server, it can take up to 1 second to send an email.  So it could take up to 11.5 days to send a million emails at 86,400 per day.  If any one of them times out because of a bad connection, the delay is usually 60 seconds until it stops trying.
crazywolf2010Author Commented:
Hi DaveBaldwin,
Many thanks for the details. Currently we use a 3rd party gateway. I have done some configuration for them and they can send 1 Million emails in less than 24 hours. They use 8 dedicated IPs over 2 dedicated windows MTA servers to forward these emails.
I don't have access to their entire system so I am not sure what technology they use.

It's possible with very minimal hardware but  your suggestion related to ISP may be right. I will check that out now.

Dave BaldwinFixer of ProblemsCommented:
8 IPs and two dedicated servers does not sound like minimal hardware to me.  The companies who send bulk email for a living have staffs of engineers to keep it running and off the blacklists.  They also have agreements with the major email services to get their emails thru.  

If you set up a new server on a new IP address, it is most likely that everything to Hotmail/Livemail will bounce at first because they require you to build up 'reputation' with them.  Or possibly pay them to get your emails delivered.  Yahoo and Gmail will be only a little friendlier.  Gmail has been known to block emails simply because they feel you are sending too many too fast.  And Yahoo just likes to bounce things for no apparent reason at all.

These services and Comcast, Charter, and Time-Warner (Roadrunner) are often more concerned with blocking spam than with letting your email thru.  That's because something over 80% of email is spam and they would rather block it than listen to the complaints from their customers.  You should not think that sending bulk emails will be easy.
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