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Recently i have been working on a popular web app that currently has around 70k members and a lot of traffic, i migrated the site to a new extra large EC2 instance and it seems to be a massive improvement, the site is a lot faster now and all images are stored on S3 to lessen the burden for the instance...

I have found that the bottleneck is now emails, the app currently sends a lot of emails, notifications on activity from users mostly, similar to the ones you get from Facebook when activity has occurred but their are reports of some users not getting emails such as verification when signing up etc and also we hit the SMTP limit on EC2 within less than a day of being on the new server proper (after DNS had resolved and users began using the site again)

I am just wondering what is the next step i could take scalability wise, the site is currently just using the built in php mail function, what can i do to ensure no problems occur with the site and the emails being delivered, would a dedicated email server be the next step ? how would that integrate with the current site ?

Any help that you could offer would be very useful...

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Do you have a local smtpd? – 3molo Mar 18 '11 at 13:15
Yeah, i was just reading about google apps (which i currently use personally) and it seems you can use google apps SMTP server to send email, could that be a good option ? – David Mar 18 '11 at 13:19
up vote 3 down vote accepted

You can use Amazon Simple Email Service.

Or have your dedicated email server somewhere else. (I noticed amazon IPs mostly in spam blacklist)

Or engage a provider that provide email server for this service

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Amazon SES does seem like a good idea but could become expensive, don't know the exact numbers of emails sent every day but it is a LOT more than the 2000 free emails allowed.. – David Mar 18 '11 at 14:09

You are correct. Your next step will be to set up your own mail server, or have someone host it for you. Having a dedicated server that can handle queuing and multiple messages per connection will also be handy for increased efficiency.

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Thanks for the suggestion, would you suggest something like postfix or a different one ? – David Mar 18 '11 at 14:10
Postfix, together with add-ons like DKIM, will be fine for a dedicated mail relay. It's fast, secure and highly configurable. But sending mail is complex job that will take time and effort to set up and keep working. If your sanity is worth anything, I would suggest looking at relay services like,,, etc. They will take care of the hard work, such as bounces and unsubscribes, blacklist delisting, DKIM and IP reputation for a reasonable price. – Martijn Heemels Jul 23 '11 at 1:50

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