The customers reach out to us with the concern that from a single delivery, as single recipient received the same message multiple times (duplicate messages).
This can be an issue at either Adobe Campaign's end or the ISP's end.
As a first step, secure the below if possible:
- MTA Child logs for the day/timeframe when this was observed.
- The actual messages (not forwarded) from the end recipients.
What to check at Adobe's end if the above data is available?
- First confirm that if the delivery had only one broadlog for the recipient in question.
- If yes, then search for the email address in the MTA child logs. If there is more than one occurrence, then review the status of each attempt.
- In most cases, it is either attempted multiple times as we received bounce message back in every try, until we succeeded last.
- Or if it is only sent once per the MTA Child logs as well, then from the actual deliveries pick a sample URL (tracked) from each message, and compare the delivery ID from the parameters list of all, and see if it is actually same.
If the message was "Technically" sent only once from Campaign, then the problem is usually at ISP's end.
In some rare occasions, it happens that even though we receive only one success response, ISP could have delivered the message more than once.
If the MTA child logs indicate multiple sends, under all other normal conditions, then it may need further investigation with RD.