'db_smtp_port' => '587',
'db_smtp_server' => 'smtp.gmail.com',
'db_smtp_ssl' => '1',
'db_smtp_user' => 'firstname.lastname@example.org',
Running that on two sites and have no problem whatsoever, initially when i tested one of the sites it was on my laptop and yes it was sloooow but it was from my internet connection ... once uploaded to the server everything settled. Now working like a charm.
Both sites are running blazing fast no delay when sending mail, may be you should investigate the problem not in GT side but in hosting provider?
Edit: I should mention i'm running GLinks 3.3.0
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