If there is a mass sending of e-mails, the further sending of e-mails via the e-mail inbox is blocked in order to prevent the respective server from ending up on a spam list.
If it is a matter of sending e-mails that you have not triggered yourself, you should take the following measures.
The sending of e-mails is limited to a sufficient limit for regular company e-mail traffic.
If you frequently send large quantities of newsletters or the like to your customers, this should not take place on a web hosting package.
On a web hosting several customers share the same server. If in such a case a customer with a mass mailing makes sure that the server ends up on a blacklist, not only this but also all other customers on the server are affected.
For the dispatch of newsletters, providers should be used who have specialized in this service.
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