As they struggle to hold back spam, at any time within the framework of "blacklisting", ISPs may block any sending of messages that look suspect due to their volumes or to their contents. The sender is then placed on a blacklist that is read by all the major actors of the industry : the blacklisted sender will often be unable to create any other emailing campaigns anywhere on the network. To avoid this rejection, all senders need to check whether they respect the latest technical and syntactic rules.
Most technical problems come from a poor configuration of the IP addresses or of the servers used for the campaign. A too intense sending rhythm or a failure to be identified by the SPF or the DKIM triggers preventive blocking by ISPs. An excellent alternative solution is to resort to an emailing professional person so as to make sure that one's messages are properly routed. You also need to reduce the rejection risks related to the insufficient treatment of the complaints that were filed or to the sendings that do not respect the opt-in regulation.
Apart from these automatic blockage procedures, addressees play an important role in the "blacklisting" of some campaigns, which are sometimes viewed as spam because of their content or of their display. Therefore, it is important to pay attention to the editorial and graphical qualities of the message. Several elements will strengthen the Internet user's trust : the explicit mention of the sender, the presence of customised and concise topics, the existence of an unsubscription link or the limitation of the vocabulary that corresponds to spam according to people.
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