Hi, When i sent emails from my domain on ISPCONFIG,most of the recipients recieves my emails, but some of them are not. When i dig in i found out most of the non-receivers using Barracuda spam filter, i checked with one of it and on Barracuda GUI it only says "Rejected",there is no any additional error code or anything, my isp defined a reverse record to my domain and seems like i don't have any problem with reverse record. Is there anything else i can do to get better smtp results/delivery rate?
Check if Barracuda has blacklisted your e-mailserver IP address. Further measures to more reliably deliver e-mails: set up SPF and DKIM, set up certificate for postfix. Check the reverse name service record, if you ISP just says it is OK and you do not check it yourself, then ... There is link to DNS tutorial in my signature, it explains how to test name service is working.
