Strange activation emails

[tL0z]

SMF Version: SMF 1.1.2
Hello,

Some members are complaining of the activation emails. Here is one activation email sent to a member:
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Why doesn't the email appear correctly? How can I fix this?

I've my forum in portuguese.

Thanks

[redone]

Which email client are they using to view these activation emails? Are these web based such as Yahoo, Hotmail etc?

[tL0z]

One user is using the webclient of www.sapo.pt

[redone]

Can you indicate which client causes the most issues?  

[tL0z]

Only this user told me the client he uses. 

[H]

Did you get any problems before upgrading to 1.1.2? (1.1.2 contained many changed to e-mails to fix certain mail clients)

Please ask the member if they can post the full e-mail including headers (if possible)