You'll find some of these mails will get bounced back to you as undeliverable, where users have enabled a setting that rejects mail as spam if it has a large number of recipients. There will be other cases where it just gets rejected as spam anyway and you never know about it.
By the time you've finished sorting all this out and resending the mail to those who initially rejected it, you may find it would have been less time-consuming to send it to just a few of them at a time. With 180 recipients that would not take too long using copy/paste. It rather depends how important you consider your mailshot to be.
If you decide you can live with a reasonable proportion of cases where it is rejected, you could use one of the apps mentioned but I would suggest you send it to all recipients as "Bcc" rather than "To". This should help avert some of it being marked as spam, and it will prevent the more annoying of your contacts from hijacking your address list and using it for their own purposes.