Wishing to send an email to about 20,000 recipients.
Our own SMTP server used for transactional emails I believe is well trusted, we've not heard of deliverability problems, mails go to gmail/yahoo fine. DKIM, SPF, DomainKeys all set up, etc.
What program should we use to send the email? Would people recommend bulk email software like Sendblaster? Would this handle unsubscribes, etc?
Send via SMTP server or connect direct to theirs? Know some of this software can connect directly to the the recipients SMTP server. Is this advisable or is sending via a trusted SMTP server better?
Use our own SMTP server vs provider like SendGrid/Critsend? Presume if we were using bulk email software we'd have to connect to a SMTP service. Are we best sending using one of these services or our own server? My thinking is the bulk sender providers may not have sent emails before to the people we're sending to and as such perhaps our server has better reputation?
If our SMTP server, what software (Windows)? Currently using SmarterMail, is this up to it or should
Update: https://www.senderscore.org/ reports our mail server IP with a score of 99, low delivery risk and very low volume.
Edit: thanks for the answers so far. Providers like MailChimp are just too expensive for one off emails. Plus they don't seem to like bought lists - in the UK this is fine if the data is collected lawfully under the List Warranty Register - http://www.dma.org.uk/information/ind-listintro.asp