[Dovecot] Timeout when downloading messages

Hi to All Gurus, Im having some problem with my mail server. Sending works perfectly but the problem is when my clients are receiving theyre mails. For example theyre downloading 20 mails, somehow when it reaches to 12 it disconnectes. Or the outlook client pops up some messages saying connection timeout? Im using dovecot and postfix for my mails server.

tia

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