We host a website that alerts subscribers (who voluntarily sign up) when an agency posts a new opening. These postings happen very infrequently (maybe 6-10 times a year). Each time a posting is uploaded, we send an email to each subscriber alerting them a new posting has been made. We have approximately 75,000 subscribers. Unfortunately, when the postings do come in, they come in all at once so we may send an email a day for 5 days, and then none for the next 4 months.
We are rewriting the website and would like to offload the sending of emails to a third party. I can't find any email service that is on-demand like this - they all seem to be subscription based and that will not service our needs because one month, we may send 450,000 emails and then not send anything for 4 months.
Does anybody have any suggestions? I am looking at Amazon SES, but am trying to stay away from them due to the cascading charges to do it properly (needing to use other AWS services). Constant Contact, Sendgrid, Mandrill, SocketLabs, MailChimp all seem to not be quite right for what we need.
Any other design choices we can make here to maybe make them work? By law, these are time limited postings so notification emails do need to be sent in a timely manner.
Edit - these are simple text emails that just state there is a new posting and to go to the website if interested.
