Mail relays or SMTP services for use in code

I'm looking to start using an SMTP or mail relay service. I've found quite a few out there, but I'm not sure if there are advantages to one vs another. The only requirements I have are:

• can 开发者_运维百科send "from" more than 1 domain (possibly >20 for all the different sites I work on)
• can pay for a higher limit (I may need to send as many as 15000 in 1 day, although the average is <500)
• can send from PHP (although I doubt this will be a problem as most are compatible with any language)

I'm okay with an SMTP service, mail relay service or a site that uses a custom API, although an API would make the conversion more difficult.

Reasons for wanting to do this:

• I don't want to host any mail services my self as they just cause head aches
• I don't have to worry about being blacklisted. If they are blacklisted they will know about it and have the knowledge to get it fixed.
• Reporting on if emails have gone through would be nice.

I'm not sure why you would need this. If you read the proper RFCs (822, 2822, 823, 2823), you should be able to connect to any given site directly using SMTP. You need to be a little careful with Line Endings (should always be CRLF), and should probably add mail.add_x_header = OFF to your php.ini.

However, if you need a relay, I recommend using a spam filtering provider, as then you have protection from being blacklisted due to spammers abusing email-generating forms. I would recommend Red Condor for this task, but that is only because I work there, and know that we can handle it.

I've started using Mandrill and found it to be a great, reliable service provided by MailChimp that includes enough for most sites to use for free. Easy to setup, but also has a lot more functionality available.