I just noticed my ISP blocked both direction for port 25. Does that mean port 25 is for both sending or receiving email? ( As email servers , transferring emails in-between) among Used to think it is for sending only.

  • 1
    how did you came to conclusion port 25 is blocked by your ISP?
    – SeanClt
    Mar 29, 2016 at 2:50

1 Answer 1


Port 25 is for sending and receiving email between servers. For mail on a client like Thunderbird, for the most part you'll be using 110 or 143 (POP3 or IMAP) to receive email, and port 465 or 587 (SMTP over TLS-on-connect or SMTP with STARTTLS).

  • @NathaneilCapital If my answer helped you, please upvote and accept. May 31, 2018 at 18:05
  • More specifically, port 25 is the default port for SMTP.
    – Keltari
    Dec 4, 2018 at 21:10
  • @Keltari For servers, yes, but most mail clients I've seen default to 587. Dec 4, 2018 at 21:25

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