query hangs

Can anyone please tell me why the following query hangs?
This is a part of a large query.

explain
select *
from vtiger_emaildetails
inner join vtiger_vantage_email_track on vtiger_emaildetails.emailid =
vtiger_vantage_email_track.mailid
left join vtiger_seactivityrel on vtiger_seactivityrel.activityid =
vtiger_emaildetails.emailid

QUERY
PLAN
-------------------------------------------------------------------------------------------------------------------------
Merge Left Join (cost=9500.30..101672.51 rows=2629549 width=506)
Merge Cond: ("outer".emailid = "inner".activityid)
-> Merge Join (cost=9500.30..11658.97 rows=88852 width=498)
Merge Cond: ("outer".emailid = "inner".mailid)
-> Index Scan using vtiger_emaildetails_pkey on
vtiger_emaildetails (cost=0.00..714.40 rows=44595 width=486)
-> Sort (cost=9500.30..9722.43 rows=88852 width=12)
Sort Key: vtiger_vantage_email_track.mailid
-> Seq Scan on vtiger_vantage_email_track
(cost=0.00..1369.52 rows=88852 width=12)
-> Index Scan using seactivityrel_activityid_idx on
vtiger_seactivityrel (cost=0.00..28569.29 rows=1319776 width=8)
(9 rows)

select relname, reltuples, relpages
from pg_class
where relname in
('vtiger_emaildetails','vtiger_vantage_email_track','vtiger_seactivityrel');

relname | reltuples | relpages
----------------------------+-------------+----------
vtiger_emaildetails | 44595 | 1360
vtiger_seactivityrel | 1.31978e+06 | 6470
vtiger_vantage_email_track | 88852 | 481
(3 rows)