Bulk email without duplicates

[JasonByrne]

Imagine a member has selected groups and sub-categories he is interested in.

I want to send an announcement to those who selected either of those groups and sub-categories.

Example: In a city made of the global main city, several boroughs and matters.
I would also have groups that are borough-matter specific.

The user can select:

• A specific matter (Which as a general group),
• A group in his borough for this matter,
• A group in two other borough for this matter,
• A second specific matter (Which as a general group),
• All groups in all boroughs for this matter,
• The main group for the main city;

If I wish to send an email to one or more groups or subcategories in these groups, some users might end up receiving more than one email of the same announcement, especially if the person selected the main city group that would forward the info from all boroughs and matters, plus some subgroups, etc.

The question: How can I prepare a mailing touching more than one targeted group and sub-categories list, duplicate-free, and send that message?

1. Do I need to use an external script?
2. Do I need an external email processor?

Thanks

[LanestIo]

Merge and deduplicate these lists, either manually or using a script.

[Sanidly]

I’ve been using a warm-up tool to slowly rebuild trust with inbox providers, and it helped me dodge issues like getting tossed onto an email blacklist, which can tank deliverability fast. The gradual sending schedule and positive engagement signals made a noticeable difference for me, especially as I scaled volume without freaking out the filters.