Hello, I use ISPConfig for a long time and usually, years ago I did not use the relayhost and many of the emails I sent reached the spam folder of the recipient. Now I wm using the relayhost with SendGrid, but still some mails reach the spam folder. Are there any option to avoid this problem? I use: ISPConfig 3.2.5 Ubuntu 18.04.4 I have a static IP I do not have the option to set a reverse DNS, because my internet supplier does not offer this service. Thanks
Various mail providers offer guidance on improving your email delivery, follow those and it will help with other providers as well. There are many general things you can do, eg setup SPF/dkim/dmarc, ensure your server doesn't send out a lot of spam, check if it is on blacklists and get it delisted, ensure your reverse dns is setup and matches your mail name, setup feedback loop added with large mail providers and respond to abuse complaints.
I think it's best to move your server to a VPS provider that supports things like rDNS to improve deliverability for your own IP.
It can be just one main cause, or could be numerous/many. If SendGrid's servers have reverse dns setup (I'd expect they would, but who knows) it might not be that at all.
You need to make sure you have the proper SPF/DKIM/DMARC set, What SPF you should use sendgrid can tell you. Good if you can use '-a'. Enable DKIM with sendgrid and put in the DKIM key you will get from sendgrid to your DNS zone. When you are sure SPF and DKIM works, you can test it here https://dkimvalidator.com, the last step is to enable DMARC. You can get guidance at https://dmarc.postmarkapp.com and they also provide a free service to gather the reports and send you a weekly readable report. It takes seconds to enable the service and it will tell you what DMARC record to put in your DNS zone. When you have done all this, there is nothing more you can do, except dont send spam. However, sendgrid has a terrrible reputation becuase thay have had poor control over spam sent from them. They have had (have?) security issues which has made it possible to retrieve their customers credentials and these accounts have been used for sending spam/malware. This has been organized in large scale and it is possible to purchase these hacked accounts. Google it and you will find. There are ISP's that block sendgrid, and man spam protection services are suspicious of mail sent from sendgrid. There are other services than sendgrid, for example postmarkapp.com and mailgun.com, the latter has a nice flexible plan. Both are US companies, if you are a EU company and hence need to fulfill GDPR, I would say you should use a EU company for this service. Example of these are sendinblue.com, rapidmail.com and flowmailer.com.
