Here's a few hints/tips from Bob Frady on how to improve your deliverability:
- Regularly mail your file - Constant communication with your file is the key to building your reputation at ISPs.
- Aggressively handle opt-outs & bounces - This is probably the single most important thing you can do to improve deliverability.
- Use an ESP
- Clean up your code - It's amazing how many companies still sent crappily-coded HTML to recipients. Stop with the Front Page templates and have a professional review performed.
- Use dedicated IPs. A lot of them. The key is to have a range of IPs that you use - if one gets "blacklisted", then you swap in new and cleaner IPs to get your mail through.
- When in doubt, slow down - Throttling your email sends can help prevent some basic ISP blocks.
- Send a confirmation email - Double-opt in is (usually) overkill, especially for sites where you're not doing much except signing up to get email. That said, it's still a great idea to send a confirmation email to the listed address.
Read the entire blog post here: Direct Marketing Central: Email Deliverability.
While I agree on point #5, I often come across clients here in Europe that have email lists with only a couple of thousand email addresses at max. In this case, it often doesn't make sense to have their own IP address because they don't send enough volume to ever warm up that IP address - let alone have multiple IP addresses.
Read Jeanne Jennings article on the subject of choosing between a dedicated or shared IP.
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