High email bounce rate in Asian countries?

Where is the client getting his e-mail list from ? It could be bad address or the headline looks like spam and never leaves the spam folder. Most likely Constant Contact is not your problem. Unless you are targeting area 's they do not cover.

First things first: Change your target audience, change your copy! Not the email system!!

Copy and audience is something you need to take a great care of when sending out emails and that's why most email programs offer segmentation among your email lists.

Do not send email to more than 500 people at once, if you don't know their interest. Suppose you have 10,000 real estate agents' emails, hand picked, 100% verified. Even though, you can't directly sell them your real estate fund and have them to invest into it.

On an average, it takes 8-9 emails before average prospect would purchase anything you are offering. So do your best test on small amount of specific target audience.

It doesn't matter if it is Asia or Europe or America, things are global when it comes to email funnel.

Have a deep look into the email list, email funnel, copy, and then decide a series of tests.

Here is what I did for my client who is a customer service professional with a 15k big list of emails in his campaign, and had issues with spam score and low opening rate:

#1 - Changed 'from' email address:

He was sending emails from a general email, say info @ hisdomain.com

I changed it to hisname @ hisdomain.com since he was highly recognized personal brand.

#2 : Identified personal emails from the list, and thrown out business emails like info@ or team@ or support@ or hello@ or contact@ etc. Using a simple find and highlight feature of Excel.

#3 : Planned a series of 7 emails just to introduce my client to these ~8k people, with one goal - they must visit the cta links atleast once during this 7 email time period.

#4 : Included personal photos of my client, not published anywhere but just in the 5th email of this series with headline : Hey (first name), meet my family!

Included a one to one conversation type copy in this email, with his photos off course, and a link to his personal website ( not the business one) where he used to share his travel adventures!

The results:

48% increase in opening rate!

Specific to the 5th email, which was opened at 76% out of ~6500 audience. Yeah, ~1500 people unsubscribed before the 5th email, but who cares!!

I don't know how many people purchased his online courses or invited him for speaking, since we were not tracking email leads in this campaign.

From my experience managing email campaign for this client, I would say, keep it simple, engaging, and make sure to provide a value or satisfy the need of your prospects.

I wish you very well my friend!

It is not a platform's fault, rather a very poor quality list. I would rather recommend verifying the email list of the client, with an email verification tool, like usebouncer.com.
Good luck!