My client need to send 500 or 1000 e-mails to a list of registered members that subscribe to mailing list, can I marked as spammer and have problems with my shared ip blacklisted on spam lists or spammer in gmail, yahoo, outlook?
What the best way to send these e-mails from my server without risks of being marked as spam or get my ip black listed? Or I recommend them to not do that in any way?
You can send an email to 1000 different users. A lot of companies send millions of emails per month !
Users can mark the email as spam if you send it without their mutual consent or send 1000 mails to each, obviously ! But in your question you explain that your users have given their consent because they are subscribed to your mailing list, so thats good.
It depends mainly on your mail content. There are a plenty of different reasons that your content can be marked as spam.
There are a lot of words which can marked your mail as spam by the mail client. a non exhaustive words list : https://blog.hubspot.com/blog/tabid/6307/bid/30684/the-ultimate-list-of-email-spam-trigger-words.aspx
You can use service like MailChimp or SendGrid to send huge amount of emails. They have free tier plan to try their service.
e.g with SendGrid
Send up to 40,000 emails for the first 30 days and 100 emails per day free forever
with MailChimp
Forever Free Up to 2,000 subscribers and 12,000 emails per month
Moreover they have a nicely done dashboard with a lot of information about your sent emails (spam report, devices, clicked mails, opened mails etc..)
You can use a service different for your marketing mails and your transactional emails. So marketing emails don't impact the reputation of your transactional emails (they are more important than marketing mails)