The basis of your activities should be primarily ensuring that you have an up to date database of contacts. The statistics of rejected addresses that you get after each mailing can help you with that.
It is good to send out messages to contacts who might actually be interested in them, that’s why it’s so important to properly create mailing groups. The better you target your message, the better results you will achieve. What's more, it allows you to build better relationships with your customers. If you don’t properly target your messages, they may end up in spam.
For some press offices (or simply domains), it is enough that a few people will mark you as spam and your emails will end up in spam for each address in that domain.
Another important issue are the titles of emails. On the Internet, you can find a list of phrases that spam filters are sensitive to. Here is an example list. The use of these phrases can result in an automatic flagging of your messages as spam, even if the recipient does not mark your messages as such.
A good practice is also asking your recipients to add your address to the address book. This way, your emails will always get to these addresses.
Also, pay attention to the number of additional elements in mailings, such as graphics, additional links, bold text, italics, etc. Emails sent from Prowly are very simple, in order not to contain too many HTML tags, which are placed on an email because of elements such as those mentioned above. Remember never to send emails that contain only a link or just a graphic and a link because they carry a huge risk of being automatically marked as spam.